diff --git a/Documentation/rest-api-changes.txt b/Documentation/rest-api-changes.txt
index f508a83..49ebb49 100644
--- a/Documentation/rest-api-changes.txt
+++ b/Documentation/rest-api-changes.txt
@@ -852,9 +852,17 @@
 
 Rebases a change.
 
+Optionally, the parent revision can be changed to another patch set through the
+link:#rebase-input[RebaseInput] entity.
+
 .Request
 ----
   POST /changes/myProject~master~I3ea943139cb62e86071996f2480e58bf3eeb9dd2/rebase HTTP/1.0
+  Content-Type: application/json;charset=UTF-8
+
+  {
+    "base" : "1234",
+  }
 ----
 
 As response a link:#change-info[ChangeInfo] entity is returned that
@@ -2200,9 +2208,17 @@
 
 Rebases a revision.
 
+Optionally, the parent revision can be changed to another patch set through the
+link:#rebase-input[RebaseInput] entity.
+
 .Request
 ----
   POST /changes/myProject~master~I3ea943139cb62e86071996f2480e58bf3eeb9dd2/revisions/674ac754f91e64a0efb8087e59a176484bd534d1/rebase HTTP/1.0
+  Content-Type: application/json;charset=UTF-8
+
+  {
+    "base" : "1234",
+  }
 ----
 
 As response a link:#change-info[ChangeInfo] entity is returned that
@@ -3877,6 +3893,21 @@
 outcome of the fix.
 |===========================
 
+[[rebase-input]]
+=== RebaseInput
+The `RebaseInput` entity contains information for changing parent when rebasing.
+
+[options="header",width="50%",cols="1,^1,5"]
+|===========================
+|Field Name    ||Description
+|`base`        |optional|
+The new parent revision. This can be a ref or a SHA1 to a concrete patchset. +
+Alternatively, a change number can be specified, in which case the current
+patch set is inferred. +
+Empty string is used for rebasing directly on top of the target branch,
+which effectively breaks dependency towards a parent change.
+|===========================
+
 [[related-change-and-commit-info]]
 === RelatedChangeAndCommitInfo
 
diff --git a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/PushOneCommit.java b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/PushOneCommit.java
index 428a19c..74f9f80 100644
--- a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/PushOneCommit.java
+++ b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/PushOneCommit.java
@@ -215,6 +215,10 @@
           queryProvider.get().byKeyPrefix(commit.getChangeId()));
     }
 
+    public PatchSet getPatchSet() throws OrmException {
+      return getChange().currentPatchSet();
+    }
+
     public PatchSet.Id getPatchSetId() throws OrmException {
       return getChange().change().currentPatchSetId();
     }
diff --git a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/api/change/ChangeIT.java b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/api/change/ChangeIT.java
index 94d564d..86c2c1f 100644
--- a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/api/change/ChangeIT.java
+++ b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/api/change/ChangeIT.java
@@ -23,6 +23,7 @@
 import com.google.gerrit.acceptance.NoHttpd;
 import com.google.gerrit.acceptance.PushOneCommit;
 import com.google.gerrit.extensions.api.changes.AddReviewerInput;
+import com.google.gerrit.extensions.api.changes.RebaseInput;
 import com.google.gerrit.extensions.api.changes.ReviewInput;
 import com.google.gerrit.extensions.client.ChangeStatus;
 import com.google.gerrit.extensions.client.ListChangesOption;
@@ -32,6 +33,7 @@
 import com.google.gerrit.extensions.common.RevisionInfo;
 import com.google.gerrit.extensions.restapi.ResourceConflictException;
 import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.PatchSet;
 
 import org.eclipse.jgit.lib.Constants;
 import org.junit.Test;
@@ -110,6 +112,49 @@
         .rebase();
   }
 
+  @Test
+  public void rebaseChangeBase() throws Exception {
+    PushOneCommit.Result r1 = createChange();
+    PushOneCommit.Result r2 = createChange();
+    PushOneCommit.Result r3 = createChange();
+    RebaseInput ri = new RebaseInput();
+
+    // rebase r3 directly onto master (break dep. towards r2)
+    ri.base = "";
+    gApi.changes()
+        .id(r3.getChangeId())
+        .revision(r3.getCommit().name())
+        .rebase(ri);
+    PatchSet ps3 = r3.getPatchSet();
+    assertThat(ps3.getId().get()).is(2);
+
+    // rebase r2 onto r3 (referenced by ref)
+    ri.base = ps3.getId().toRefName();
+    gApi.changes()
+        .id(r2.getChangeId())
+        .revision(r2.getCommit().name())
+        .rebase(ri);
+    PatchSet ps2 = r2.getPatchSet();
+    assertThat(ps2.getId().get()).is(2);
+
+    // rebase r1 onto r2 (referenced by commit)
+    ri.base = ps2.getRevision().get();
+    gApi.changes()
+        .id(r1.getChangeId())
+        .revision(r1.getCommit().name())
+        .rebase(ri);
+    PatchSet ps1 = r1.getPatchSet();
+    assertThat(ps1.getId().get()).is(2);
+
+    // rebase r1 onto r3 (referenced by change number)
+    ri.base = String.valueOf(r3.getChange().getId().get());
+    gApi.changes()
+        .id(r1.getChangeId())
+        .revision(ps1.getRevision().get())
+        .rebase(ri);
+    assertThat(r1.getPatchSetId().get()).is(3);
+  }
+
   private Set<Account.Id> getReviewers(String changeId) throws Exception {
     ChangeInfo ci = gApi.changes().id(changeId).get();
     Set<Account.Id> result = Sets.newHashSet();
diff --git a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/change/ActionsIT.java b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/change/ActionsIT.java
index 4acec9a..afcd5d0 100644
--- a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/change/ActionsIT.java
+++ b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/change/ActionsIT.java
@@ -43,7 +43,8 @@
     String changeId = createChangeWithTopic("foo1").getChangeId();
     Map<String, ActionInfo> actions = getActions(changeId);
     assertThat(actions).containsKey("cherrypick");
-    assertThat(actions).hasSize(1);
+    assertThat(actions).containsKey("rebase");
+    assertThat(actions).hasSize(2);
   }
 
   @Test
@@ -51,8 +52,7 @@
     String changeId = createChangeWithTopic("foo1").getChangeId();
     approve(changeId);
     Map<String, ActionInfo> actions = getActions(changeId);
-    assertThat(actions).containsKey("cherrypick");
-    assertThat(actions).containsKey("submit");
+    commonActionsAssertions(actions);
     if (isSubmitWholeTopicEnabled()) {
       ActionInfo info = actions.get("submit");
       assertThat(info.enabled).isTrue();
@@ -62,8 +62,6 @@
     } else {
       noSubmitWholeTopicAssertions(actions);
     }
-    // no other actions
-    assertThat(actions).hasSize(2);
   }
 
   @Test
@@ -73,10 +71,7 @@
     // create another change with the same topic
     createChangeWithTopic("foo2").getChangeId();
     Map<String, ActionInfo> actions = getActions(changeId);
-    assertThat(actions).containsKey("cherrypick");
-    assertThat(actions).containsKey("submit");
-    // no other actions:
-    assertThat(actions).hasSize(2);
+    commonActionsAssertions(actions);
     if (isSubmitWholeTopicEnabled()) {
       ActionInfo info = actions.get("submit");
       assertThat(info.enabled).isNull();
@@ -96,10 +91,7 @@
     String changeId2 = createChangeWithTopic("foo2").getChangeId();
     approve(changeId2);
     Map<String, ActionInfo> actions = getActions(changeId);
-    assertThat(actions).containsKey("cherrypick");
-    assertThat(actions).containsKey("submit");
-    // no other actions:
-    assertThat(actions).hasSize(2);
+    commonActionsAssertions(actions);
     if (isSubmitWholeTopicEnabled()) {
       ActionInfo info = actions.get("submit");
       assertThat(info.enabled).isTrue();
@@ -128,6 +120,13 @@
     assertThat(info.title).isEqualTo("Submit patch set 1 into master");
   }
 
+  private void commonActionsAssertions(Map<String, ActionInfo> actions) {
+    assertThat(actions).hasSize(3);
+    assertThat(actions).containsKey("cherrypick");
+    assertThat(actions).containsKey("submit");
+    assertThat(actions).containsKey("rebase");
+  }
+
   private PushOneCommit.Result createChangeWithTopic(String topic) throws GitAPIException,
       IOException {
     PushOneCommit push = pushFactory.create(db, admin.getIdent());
diff --git a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/RebaseInput.java b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/RebaseInput.java
new file mode 100644
index 0000000..5f4a014
--- /dev/null
+++ b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/RebaseInput.java
@@ -0,0 +1,19 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.extensions.api.changes;
+
+public class RebaseInput {
+  public String base;
+}
diff --git a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/RevisionApi.java b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/RevisionApi.java
index 202699c..b940cc9 100644
--- a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/RevisionApi.java
+++ b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/RevisionApi.java
@@ -34,6 +34,7 @@
   void publish() throws RestApiException;
   ChangeApi cherryPick(CherryPickInput in) throws RestApiException;
   ChangeApi rebase() throws RestApiException;
+  ChangeApi rebase(RebaseInput in) throws RestApiException;
   boolean canRebase();
 
   void setReviewed(String path, boolean reviewed) throws RestApiException;
@@ -94,6 +95,11 @@
     }
 
     @Override
+    public ChangeApi rebase(RebaseInput in) throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
     public boolean canRebase() {
       throw new NotImplementedException();
     }
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/GerritCss.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/GerritCss.java
index c919c6b..2844b5e 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/GerritCss.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/GerritCss.java
@@ -158,6 +158,8 @@
   String projectFilterLabel();
   String projectFilterPanel();
   String projectNameColumn();
+  String rebaseContentPanel();
+  String rebaseSuggestBox();
   String registerScreenExplain();
   String registerScreenNextLinks();
   String registerScreenSection();
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/Actions.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/Actions.java
index 93881d2..37b90c4 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/Actions.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/Actions.java
@@ -176,7 +176,7 @@
 
   @UiHandler("rebase")
   void onRebase(@SuppressWarnings("unused") ClickEvent e) {
-    RebaseAction.call(changeId, revision);
+    RebaseAction.call(rebase, project, changeInfo.branch(), changeId, revision);
   }
 
   @UiHandler("submit")
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/RebaseAction.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/RebaseAction.java
index b1ad583..ffe9627 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/RebaseAction.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/RebaseAction.java
@@ -18,17 +18,42 @@
 import com.google.gerrit.client.changes.ChangeApi;
 import com.google.gerrit.client.changes.ChangeInfo;
 import com.google.gerrit.client.rpc.GerritCallback;
+import com.google.gerrit.client.ui.RebaseDialog;
 import com.google.gerrit.common.PageLinks;
 import com.google.gerrit.reviewdb.client.Change;
+import com.google.gwt.event.logical.shared.CloseEvent;
+import com.google.gwt.user.client.ui.Button;
+import com.google.gwt.user.client.ui.PopupPanel;
 
 class RebaseAction {
-  static void call(final Change.Id id, String revision) {
-    ChangeApi.rebase(id.get(), revision,
-      new GerritCallback<ChangeInfo>() {
-        @Override
-        public void onSuccess(ChangeInfo result) {
-          Gerrit.display(PageLinks.toChange(id));
-        }
-      });
+  static void call(final Button b, final String project, final String branch,
+      final Change.Id id, final String revision) {
+    b.setEnabled(false);
+
+    new RebaseDialog(project, branch, id) {
+      @Override
+      public void onSend() {
+        ChangeApi.rebase(id.get(), revision, getBase(), new GerritCallback<ChangeInfo>() {
+          @Override
+          public void onSuccess(ChangeInfo result) {
+            sent = true;
+            hide();
+            Gerrit.display(PageLinks.toChange(id));
+          }
+
+          @Override
+          public void onFailure(Throwable caught) {
+            enableButtons(true);
+            super.onFailure(caught);
+          }
+        });
+      }
+
+      @Override
+      public void onClose(CloseEvent<PopupPanel> event) {
+        super.onClose(event);
+        b.setEnabled(true);
+      }
+    }.center();
   }
 }
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/RevertAction.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/RevertAction.java
index f9c18cd..3af97f5 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/RevertAction.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/RevertAction.java
@@ -19,7 +19,7 @@
 import com.google.gerrit.client.changes.ChangeInfo;
 import com.google.gerrit.client.changes.Util;
 import com.google.gerrit.client.rpc.GerritCallback;
-import com.google.gerrit.client.ui.CommentedActionDialog;
+import com.google.gerrit.client.ui.TextAreaActionDialog;
 import com.google.gerrit.common.PageLinks;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gwt.user.client.ui.Button;
@@ -29,7 +29,7 @@
       final String commitSubject) {
     // TODO Replace ActionDialog with a nicer looking display.
     b.setEnabled(false);
-    new CommentedActionDialog(
+    new TextAreaActionDialog(
         Util.C.revertChangeTitle(),
         Util.C.headingRevertMessage()) {
       {
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeApi.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeApi.java
index 0a29a00..1135491 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeApi.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeApi.java
@@ -216,10 +216,11 @@
     change(id).view("edit:rebase").post(in, cb);
   }
 
-  /** Rebase a revision onto the branch tip. */
-  public static void rebase(int id, String commit, AsyncCallback<ChangeInfo> cb) {
-    JavaScriptObject in = JavaScriptObject.createObject();
-    call(id, commit, "rebase").post(in, cb);
+  /** Rebase a revision onto the branch tip or another change. */
+  public static void rebase(int id, String commit, String base, AsyncCallback<ChangeInfo> cb) {
+    RebaseInput rebaseInput = RebaseInput.create();
+    rebaseInput.setBase(base);
+    call(id, commit, "rebase").post(rebaseInput, cb);
   }
 
   private static class Input extends JavaScriptObject {
@@ -260,6 +261,17 @@
     }
   }
 
+  private static class RebaseInput extends JavaScriptObject {
+    final native void setBase(String b) /*-{ this.base = b; }-*/;
+
+    static RebaseInput create() {
+      return (RebaseInput) createObject();
+    }
+
+    protected RebaseInput() {
+    }
+  }
+
   private static class SubmitInput extends JavaScriptObject {
     final native void wait_for_merge(boolean b) /*-{ this.wait_for_merge=b; }-*/;
 
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeConstants.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeConstants.java
index 2bbb429..00c4404 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeConstants.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeConstants.java
@@ -164,6 +164,11 @@
   String cherryPickCommitMessage();
   String cherryPickTitle();
 
+  String buttonRebaseChangeSend();
+  String rebaseConfirmMessage();
+  String rebasePlaceholderMessage();
+  String rebaseTitle();
+
   String buttonAbandonChangeBegin();
   String buttonAbandonChangeSend();
   String headingAbandonMessage();
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeConstants.properties b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeConstants.properties
index df1e2c5..9bf3f39 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeConstants.properties
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeConstants.properties
@@ -150,6 +150,11 @@
 cherryPickCommitMessage = Cherry Pick Commit Message:
 cherryPickTitle = Code Review - Cherry Pick Change to Another Branch
 
+buttonRebaseChangeSend = Rebase
+rebaseConfirmMessage = Change parent revision
+rebasePlaceholderMessage = (subject, change number, or leave empty)
+rebaseTitle = Code Review - Rebase Change
+
 buttonRestoreChangeBegin = Restore Change
 restoreChangeTitle = Code Review - Restore Change
 headingRestoreMessage = Restore Message:
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/gerrit.css b/gerrit-gwtui/src/main/java/com/google/gerrit/client/gerrit.css
index 0d0f793..8d961ca 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/gerrit.css
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/gerrit.css
@@ -1162,6 +1162,16 @@
   white-space: nowrap;
   font-size: small;
 }
+.commentedActionDialog .rebaseContentPanel {
+  margin-left: 10px;
+  background: trimColor;
+  padding: 5px 5px 5px 5px;
+  width: 300px;
+}
+.commentedActionDialog .rebaseContentPanel .rebaseSuggestBox {
+  font-size: small;
+  width: 100%;
+}
 
 /** PatchBrowserPopup **/
 .patchBrowserPopup {
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/CherryPickDialog.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/CherryPickDialog.java
index 3813af2..00269f9 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/CherryPickDialog.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/CherryPickDialog.java
@@ -31,7 +31,7 @@
 import java.util.LinkedList;
 import java.util.List;
 
-public abstract class CherryPickDialog extends CommentedActionDialog {
+public abstract class CherryPickDialog extends TextAreaActionDialog {
   private SuggestBox newBranch;
   private List<BranchInfo> branches;
 
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/CommentedActionDialog.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/CommentedActionDialog.java
index aa32394..60b5f93 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/CommentedActionDialog.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/CommentedActionDialog.java
@@ -24,16 +24,15 @@
 import com.google.gwt.user.client.ui.FocusWidget;
 import com.google.gwt.user.client.ui.PopupPanel;
 import com.google.gwtexpui.globalkey.client.GlobalKey;
-import com.google.gwtexpui.globalkey.client.NpTextArea;
 import com.google.gwtexpui.user.client.AutoCenterDialogBox;
 
 public abstract class CommentedActionDialog extends AutoCenterDialogBox
     implements CloseHandler<PopupPanel> {
   protected final FlowPanel panel;
-  protected final NpTextArea message;
   protected final Button sendButton;
   protected final Button cancelButton;
   protected final FlowPanel buttonPanel;
+  protected final FlowPanel contentPanel;
   protected FocusWidget focusOn;
 
   protected boolean sent = false;
@@ -45,11 +44,6 @@
 
     addStyleName(Gerrit.RESOURCES.css().commentedActionDialog());
 
-    message = new NpTextArea();
-    message.setCharacterWidth(60);
-    message.setVisibleLines(10);
-    message.getElement().setPropertyBoolean("spellcheck", true);
-    setFocusOn(message);
     sendButton = new Button(Util.C.commentedActionButtonSend());
     sendButton.addClickHandler(new ClickHandler() {
       @Override
@@ -68,9 +62,8 @@
       }
     });
 
-    final FlowPanel mwrap = new FlowPanel();
-    mwrap.setStyleName(Gerrit.RESOURCES.css().commentedActionMessage());
-    mwrap.add(message);
+    contentPanel = new FlowPanel();
+    contentPanel.setStyleName(Gerrit.RESOURCES.css().commentedActionMessage());
 
     buttonPanel = new FlowPanel();
     buttonPanel.add(sendButton);
@@ -78,8 +71,10 @@
     buttonPanel.getElement().getStyle().setProperty("marginTop", "4px");
 
     panel = new FlowPanel();
-    panel.add(new SmallHeading(heading));
-    panel.add(mwrap);
+    if (heading != null) {
+      panel.add(new SmallHeading(heading));
+    }
+    panel.add(contentPanel);
     panel.add(buttonPanel);
     add(panel);
 
@@ -110,8 +105,4 @@
   }
 
   public abstract void onSend();
-
-  public String getMessageText() {
-    return message.getText().trim();
-  }
 }
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/CreateChangeDialog.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/CreateChangeDialog.java
index 2b6a866..021f39c 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/CreateChangeDialog.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/CreateChangeDialog.java
@@ -31,7 +31,7 @@
 import java.util.ArrayList;
 import java.util.List;
 
-public abstract class CreateChangeDialog extends CommentedActionDialog {
+public abstract class CreateChangeDialog extends TextAreaActionDialog {
   private SuggestBox newChange;
   private List<BranchInfo> branches;
 
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/RebaseDialog.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/RebaseDialog.java
new file mode 100644
index 0000000..58f806a
--- /dev/null
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/RebaseDialog.java
@@ -0,0 +1,119 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.client.ui;
+
+import com.google.gerrit.client.Gerrit;
+import com.google.gerrit.client.changes.ChangeInfo;
+import com.google.gerrit.client.changes.ChangeList;
+import com.google.gerrit.client.changes.Util;
+import com.google.gerrit.client.rpc.GerritCallback;
+import com.google.gerrit.client.rpc.Natives;
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gwt.event.dom.client.ClickHandler;
+import com.google.gwt.event.dom.client.ClickEvent;
+import com.google.gwt.user.client.ui.CheckBox;
+import com.google.gwt.user.client.ui.SuggestBox;
+import com.google.gwt.user.client.ui.SuggestOracle.Suggestion;
+import com.google.gwtexpui.safehtml.client.HighlightSuggestOracle;
+
+import java.util.LinkedList;
+import java.util.List;
+
+public abstract class RebaseDialog extends CommentedActionDialog {
+  private final SuggestBox base;
+  private final CheckBox cb;
+  private List<ChangeInfo> changes;
+
+  public RebaseDialog(final String project, final String branch,
+      final Change.Id changeId) {
+    super(Util.C.rebaseTitle(), null);
+    sendButton.setText(Util.C.buttonRebaseChangeSend());
+
+    // create the suggestion box
+    base = new SuggestBox(new HighlightSuggestOracle() {
+      @Override
+      protected void onRequestSuggestions(Request request, Callback done) {
+        String query = request.getQuery().toLowerCase();
+        LinkedList<ChangeSuggestion> suggestions = new LinkedList<>();
+        for (final ChangeInfo ci : changes) {
+          if (changeId.equals(ci.legacy_id())) {
+            continue;  // do not suggest current change
+          }
+          String id = String.valueOf(ci.legacy_id().get());
+          if (id.contains(query) || ci.subject().toLowerCase().contains(query)) {
+            suggestions.add(new ChangeSuggestion(ci));
+            if (suggestions.size() >= 50) { // limit to 50 suggestions
+              break;
+            }
+          }
+        }
+        done.onSuggestionsReady(request, new Response(suggestions));
+      }
+    });
+    base.setEnabled(false);
+    base.getElement().setAttribute("placeholder",
+        Util.C.rebasePlaceholderMessage());
+    base.setStyleName(Gerrit.RESOURCES.css().rebaseSuggestBox());
+
+    // the checkbox which must be clicked before the change list is populated
+    cb = new CheckBox(Util.C.rebaseConfirmMessage());
+    cb.addClickHandler(new ClickHandler() {
+      @Override
+      public void onClick(ClickEvent event) {
+        boolean checked = ((CheckBox) event.getSource()).getValue();
+        if (checked) {
+          ChangeList.next("project:" + project + " AND branch:" + branch
+              + " AND is:open NOT age:90d", 0, 1000,
+              new GerritCallback<ChangeList>() {
+                @Override
+                public void onSuccess(ChangeList result) {
+                  changes = Natives.asList(result);
+                  base.setEnabled(true);
+                }
+              });
+        } else {
+          base.setEnabled(false);
+        }
+      }
+    });
+
+    // add the checkbox and suggestbox widgets to the content panel
+    contentPanel.add(cb);
+    contentPanel.add(base);
+    contentPanel.setStyleName(Gerrit.RESOURCES.css().rebaseContentPanel());
+  }
+
+  public String getBase() {
+    return cb.getValue() ? base.getText() : null;
+  }
+
+  private static class ChangeSuggestion implements Suggestion {
+    private ChangeInfo change;
+
+    public ChangeSuggestion(ChangeInfo change) {
+      this.change = change;
+    }
+
+    @Override
+    public String getDisplayString() {
+      return String.valueOf(change.legacy_id().get()) + ": " + change.subject();
+    }
+
+    @Override
+    public String getReplacementString() {
+      return String.valueOf(change.legacy_id().get());
+    }
+  }
+}
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/TextAreaActionDialog.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/TextAreaActionDialog.java
new file mode 100644
index 0000000..d7d5d6a
--- /dev/null
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/TextAreaActionDialog.java
@@ -0,0 +1,40 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.client.ui;
+
+import com.google.gwt.event.logical.shared.CloseHandler;
+import com.google.gwt.user.client.ui.PopupPanel;
+import com.google.gwtexpui.globalkey.client.NpTextArea;
+
+public abstract class TextAreaActionDialog extends CommentedActionDialog
+    implements CloseHandler<PopupPanel> {
+  protected final NpTextArea message;
+
+  public TextAreaActionDialog(String title, String heading) {
+    super(title, heading);
+
+    message = new NpTextArea();
+    message.setCharacterWidth(60);
+    message.setVisibleLines(10);
+    message.getElement().setPropertyBoolean("spellcheck", true);
+    setFocusOn(message);
+
+    contentPanel.add(message);
+  }
+
+  public String getMessageText() {
+    return message.getText().trim();
+  }
+}
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java b/gerrit-server/src/main/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java
index 6b4c1a1..c36faa2 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/api/changes/RevisionApiImpl.java
@@ -23,6 +23,7 @@
 import com.google.gerrit.extensions.api.changes.DraftApi;
 import com.google.gerrit.extensions.api.changes.DraftInput;
 import com.google.gerrit.extensions.api.changes.FileApi;
+import com.google.gerrit.extensions.api.changes.RebaseInput;
 import com.google.gerrit.extensions.api.changes.ReviewInput;
 import com.google.gerrit.extensions.api.changes.RevisionApi;
 import com.google.gerrit.extensions.api.changes.SubmitInput;
@@ -179,8 +180,14 @@
 
   @Override
   public ChangeApi rebase() throws RestApiException {
+    RebaseInput in = new RebaseInput();
+    return rebase(in);
+  }
+
+  @Override
+  public ChangeApi rebase(RebaseInput in) throws RestApiException {
     try {
-      return changes.id(rebase.apply(revision, null)._number);
+      return changes.id(rebase.apply(revision, in)._number);
     } catch (OrmException | EmailException e) {
       throw new RestApiException("Cannot rebase ps", e);
     }
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/Rebase.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/Rebase.java
index 331dfe5..3f61b01 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/change/Rebase.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/Rebase.java
@@ -15,6 +15,7 @@
 package com.google.gerrit.server.change;
 
 import com.google.gerrit.common.errors.EmailException;
+import com.google.gerrit.extensions.api.changes.RebaseInput;
 import com.google.gerrit.extensions.client.ListChangesOption;
 import com.google.gerrit.extensions.common.ChangeInfo;
 import com.google.gerrit.extensions.restapi.AuthException;
@@ -23,9 +24,10 @@
 import com.google.gerrit.extensions.restapi.RestModifyView;
 import com.google.gerrit.extensions.webui.UiAction;
 import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.Change.Status;
 import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.reviewdb.server.ReviewDb;
-import com.google.gerrit.server.change.Rebase.Input;
 import com.google.gerrit.server.changedetail.RebaseChange;
 import com.google.gerrit.server.project.ChangeControl;
 import com.google.gerrit.server.project.InvalidChangeOperationException;
@@ -35,27 +37,34 @@
 import com.google.inject.Provider;
 import com.google.inject.Singleton;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.io.IOException;
 
 @Singleton
-public class Rebase implements RestModifyView<RevisionResource, Input>,
+public class Rebase implements RestModifyView<RevisionResource, RebaseInput>,
     UiAction<RevisionResource> {
-  public static class Input {
-  }
+
+  private static final Logger log =
+      LoggerFactory.getLogger(Rebase.class);
 
   private final Provider<RebaseChange> rebaseChange;
   private final ChangeJson json;
+  private final Provider<ReviewDb> dbProvider;
 
   @Inject
-  public Rebase(Provider<RebaseChange> rebaseChange, ChangeJson json) {
+  public Rebase(Provider<RebaseChange> rebaseChange, ChangeJson json,
+      Provider<ReviewDb> dbProvider) {
     this.rebaseChange = rebaseChange;
     this.json = json
         .addOption(ListChangesOption.CURRENT_REVISION)
         .addOption(ListChangesOption.CURRENT_COMMIT);
+    this.dbProvider = dbProvider;
   }
 
   @Override
-  public ChangeInfo apply(RevisionResource rsrc, Input input)
+  public ChangeInfo apply(RevisionResource rsrc, RebaseInput input)
       throws AuthException, ResourceNotFoundException,
       ResourceConflictException, EmailException, OrmException {
     ChangeControl control = rsrc.getControl();
@@ -65,11 +74,52 @@
     } else if (!change.getStatus().isOpen()) {
       throw new ResourceConflictException("change is "
           + change.getStatus().name().toLowerCase());
+    } else if (!hasOneParent(rsrc.getPatchSet().getId())) {
+      throw new ResourceConflictException(
+          "cannot rebase merge commits or commit with no ancestor");
+    }
+
+    String baseRev = null;
+    if (input != null && input.base != null) {
+      String base = input.base.trim();
+      do {
+        if (base.equals("")) {
+          // remove existing dependency to other patch set
+          baseRev = change.getDest().get();
+          break;
+        }
+
+        ReviewDb db = dbProvider.get();
+        PatchSet basePatchSet = parseBase(base);
+        if (basePatchSet == null) {
+          throw new ResourceConflictException("base revision is missing: " + base);
+        } else if (!rsrc.getControl().isPatchVisible(basePatchSet, db)) {
+          throw new AuthException("base revision not accessible: " + base);
+        } else if (change.getId().equals(basePatchSet.getId().getParentKey())) {
+          throw new ResourceConflictException("cannot depend on self");
+        }
+
+        Change baseChange = db.changes().get(basePatchSet.getId().getParentKey());
+        if (baseChange != null) {
+          if (!baseChange.getProject().equals(change.getProject())) {
+            throw new ResourceConflictException("base change is in wrong project: "
+                                                + baseChange.getProject());
+          } else if (!baseChange.getDest().equals(change.getDest())) {
+            throw new ResourceConflictException("base change is targetting wrong branch: "
+                                                + baseChange.getDest());
+          } else if (baseChange.getStatus() == Status.ABANDONED) {
+            throw new ResourceConflictException("base change is abandoned: "
+                                                + baseChange.getKey());
+          }
+          baseRev = basePatchSet.getRevision().get();
+          break;
+        }
+      } while (false);  // just wanted to use the break statement
     }
 
     try {
       rebaseChange.get().rebase(rsrc.getChange(), rsrc.getPatchSet().getId(),
-          rsrc.getUser());
+          rsrc.getUser(), baseRev);
     } catch (InvalidChangeOperationException e) {
       throw new ResourceConflictException(e.getMessage());
     } catch (IOException e) {
@@ -81,6 +131,53 @@
     return json.format(change.getId());
   }
 
+  private PatchSet parseBase(final String base) throws OrmException {
+    ReviewDb db = dbProvider.get();
+
+    PatchSet.Id basePatchSetId = PatchSet.Id.fromRef(base);
+    if (basePatchSetId != null) {
+      // try parsing the base as a ref string
+      return db.patchSets().get(basePatchSetId);
+    }
+
+    // try parsing base as a change number (assume current patch set)
+    PatchSet basePatchSet = null;
+    try {
+      Change.Id baseChangeId = Change.Id.parse(base);
+      if (baseChangeId != null) {
+        for (PatchSet ps : db.patchSets().byChange(baseChangeId)) {
+          if (basePatchSet == null || basePatchSet.getId().get() < ps.getId().get()){
+            basePatchSet = ps;
+          }
+        }
+      }
+    } catch (NumberFormatException e) {  // probably a SHA1
+    }
+
+    // try parsing as SHA1
+    if (basePatchSet == null) {
+      for (PatchSet ps : db.patchSets().byRevision(new RevId(base))) {
+        if (basePatchSet == null || basePatchSet.getId().get() < ps.getId().get()) {
+          basePatchSet = ps;
+        }
+      }
+    }
+
+    return basePatchSet;
+  }
+
+  private boolean hasOneParent(final PatchSet.Id patchSetId) {
+    try {
+      // prevent rebase of exotic changes (merge commit, no ancestor).
+      return (dbProvider.get().patchSetAncestors()
+          .ancestorsOf(patchSetId).toList().size() == 1);
+    } catch (OrmException e) {
+      log.error("Failed to get ancestors of patch set "
+          + patchSetId.toRefName(), e);
+      return false;
+    }
+  }
+
   @Override
   public UiAction.Description getDescription(RevisionResource resource) {
     return new UiAction.Description()
@@ -88,30 +185,28 @@
       .setTitle("Rebase onto tip of branch or parent change")
       .setVisible(resource.getChange().getStatus().isOpen()
           && resource.getControl().canRebase()
-          && rebaseChange.get().canRebase(resource));
+          && hasOneParent(resource.getPatchSet().getId()));
   }
 
   public static class CurrentRevision implements
-      RestModifyView<ChangeResource, Input> {
-    private final Provider<ReviewDb> dbProvider;
+      RestModifyView<ChangeResource, RebaseInput> {
     private final Rebase rebase;
 
     @Inject
-    CurrentRevision(Provider<ReviewDb> dbProvider, Rebase rebase) {
-      this.dbProvider = dbProvider;
+    CurrentRevision(Rebase rebase) {
       this.rebase = rebase;
     }
 
     @Override
-    public ChangeInfo apply(ChangeResource rsrc, Input input)
+    public ChangeInfo apply(ChangeResource rsrc, RebaseInput input)
         throws AuthException, ResourceNotFoundException,
         ResourceConflictException, EmailException, OrmException {
       PatchSet ps =
-          dbProvider.get().patchSets()
+          rebase.dbProvider.get().patchSets()
               .get(rsrc.getChange().currentPatchSetId());
       if (ps == null) {
         throw new ResourceConflictException("current revision is missing");
-      } else if (!rsrc.getControl().isPatchVisible(ps, dbProvider.get())) {
+      } else if (!rsrc.getControl().isPatchVisible(ps, rebase.dbProvider.get())) {
         throw new AuthException("current revision not accessible");
       }
       return rebase.apply(new RevisionResource(rsrc, ps), input);
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/changedetail/RebaseChange.java b/gerrit-server/src/main/java/com/google/gerrit/server/changedetail/RebaseChange.java
index 9bb67ea..f80a474 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/changedetail/RebaseChange.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/changedetail/RebaseChange.java
@@ -99,6 +99,7 @@
    * @param change the change to perform the rebase for
    * @param patchSetId the id of the patch set
    * @param uploader the user that creates the rebased patch set
+   * @param newBaseRev the commit that should be the new base
    * @throws NoSuchChangeException thrown if the change to which the patch set
    *         belongs does not exist or is not visible to the user
    * @throws EmailException thrown if sending the e-mail to notify about the new
@@ -107,9 +108,9 @@
    * @throws IOException thrown if rebase is not possible or not needed
    * @throws InvalidChangeOperationException thrown if rebase is not allowed
    */
-  public void rebase(Change change, PatchSet.Id patchSetId, final IdentifiedUser uploader)
-      throws NoSuchChangeException, EmailException, OrmException, IOException,
-      InvalidChangeOperationException {
+  public void rebase(Change change, PatchSet.Id patchSetId, final IdentifiedUser uploader,
+      final String newBaseRev) throws NoSuchChangeException, EmailException, OrmException,
+      IOException, InvalidChangeOperationException {
     final Change.Id changeId = patchSetId.getParentKey();
     final ChangeControl changeControl =
         changeControlFactory.validateFor(change, uploader);
@@ -126,10 +127,17 @@
       rw = new RevWalk(git);
       inserter = git.newObjectInserter();
 
-      final String baseRev = findBaseRevision(patchSetId, db.get(),
-          change.getDest(), git, null, null, null);
-      final RevCommit baseCommit =
-          rw.parseCommit(ObjectId.fromString(baseRev));
+      String baseRev = newBaseRev;
+      if (baseRev == null) {
+          baseRev = findBaseRevision(patchSetId, db.get(),
+              change.getDest(), git, null, null, null);
+      }
+      ObjectId baseObjectId = git.resolve(baseRev);
+      if (baseObjectId == null) {
+        throw new InvalidChangeOperationException(
+          "Cannot rebase: Failed to resolve baseRev: " + baseRev);
+      }
+      final RevCommit baseCommit = rw.parseCommit(baseObjectId);
 
       PersonIdent committerIdent =
           uploader.newCommitterIdent(TimeUtil.nowTs(),