diff --git a/Documentation/user-search.txt b/Documentation/user-search.txt
index 377012a..a2dc31f 100644
--- a/Documentation/user-search.txt
+++ b/Documentation/user-search.txt
@@ -251,6 +251,16 @@
 often combined with 'branch:' and 'project:' operators to select
 all related changes in a series.
 
+[[inhashtag]]
+inhashtag:'HASHTAG'::
++
+Changes where any hashtag contains 'HASHTAG', using a full-text search.
++
+If 'HASHTAG' starts with `^` it matches hashtag names by regular
+expression patterns.  The
+link:http://www.brics.dk/automaton/[dk.brics.automaton
+library,role=external,window=_blank] is used for evaluation of such patterns.
+
 [[hashtag]]
 hashtag:'HASHTAG'::
 +
diff --git a/java/com/google/gerrit/server/index/change/ChangeField.java b/java/com/google/gerrit/server/index/change/ChangeField.java
index c1b2dc7..9a0ae75 100644
--- a/java/com/google/gerrit/server/index/change/ChangeField.java
+++ b/java/com/google/gerrit/server/index/change/ChangeField.java
@@ -179,6 +179,11 @@
       exact(ChangeQueryBuilder.FIELD_HASHTAG)
           .buildRepeatable(cd -> cd.hashtags().stream().map(String::toLowerCase).collect(toSet()));
 
+  /** Hashtags as fulltext field for in-string search. */
+  public static final FieldDef<ChangeData, Iterable<String>> FUZZY_HASHTAG =
+      fullText("hashtag2")
+          .buildRepeatable(cd -> cd.hashtags().stream().map(String::toLowerCase).collect(toSet()));
+
   /** Hashtags with original case. */
   public static final FieldDef<ChangeData, Iterable<byte[]>> HASHTAG_CASE_AWARE =
       storedOnly("_hashtag")
diff --git a/java/com/google/gerrit/server/index/change/ChangeSchemaDefinitions.java b/java/com/google/gerrit/server/index/change/ChangeSchemaDefinitions.java
index 969b071..ffccb51 100644
--- a/java/com/google/gerrit/server/index/change/ChangeSchemaDefinitions.java
+++ b/java/com/google/gerrit/server/index/change/ChangeSchemaDefinitions.java
@@ -135,9 +135,14 @@
       new Schema.Builder<ChangeData>().add(V59).add(ChangeField.MERGE).build();
 
   /** Added new field {@link ChangeField#MERGED_ON} */
+  @Deprecated
   static final Schema<ChangeData> V61 =
       new Schema.Builder<ChangeData>().add(V60).add(ChangeField.MERGED_ON).build();
 
+  /** Added new field {@link ChangeField#FUZZY_HASHTAG} */
+  static final Schema<ChangeData> V62 =
+      new Schema.Builder<ChangeData>().add(V61).add(ChangeField.FUZZY_HASHTAG).build();
+
   /**
    * Name of the change index to be used when contacting index backends or loading configurations.
    */
diff --git a/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java b/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java
index 4e3edcd..6e2f49c 100644
--- a/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java
+++ b/java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java
@@ -790,7 +790,23 @@
 
   @Operator
   public Predicate<ChangeData> hashtag(String hashtag) {
-    return new HashtagPredicate(hashtag);
+    return new ExactHashtagPredicate(hashtag);
+  }
+
+  @Operator
+  public Predicate<ChangeData> inhashtag(String hashtag) throws QueryParseException {
+    if (hashtag.startsWith("^")) {
+      return new RegexHashtagPredicate(hashtag);
+    }
+    if (hashtag.isEmpty()) {
+      return new ExactHashtagPredicate(hashtag);
+    }
+
+    if (!args.index.getSchema().hasField(ChangeField.FUZZY_HASHTAG)) {
+      throw new QueryParseException(
+          "'inhashtag' operator is not supported by change index version");
+    }
+    return new FuzzyHashtagPredicate(hashtag, args.index);
   }
 
   @Operator
diff --git a/java/com/google/gerrit/server/query/change/HashtagPredicate.java b/java/com/google/gerrit/server/query/change/ExactHashtagPredicate.java
similarity index 77%
rename from java/com/google/gerrit/server/query/change/HashtagPredicate.java
rename to java/com/google/gerrit/server/query/change/ExactHashtagPredicate.java
index 1fe4af4..a6526f7 100644
--- a/java/com/google/gerrit/server/query/change/HashtagPredicate.java
+++ b/java/com/google/gerrit/server/query/change/ExactHashtagPredicate.java
@@ -14,19 +14,23 @@
 
 package com.google.gerrit.server.query.change;
 
+import com.google.common.base.Strings;
 import com.google.gerrit.server.change.HashtagsUtil;
 import com.google.gerrit.server.index.change.ChangeField;
 
-public class HashtagPredicate extends ChangeIndexPredicate {
-  public HashtagPredicate(String hashtag) {
+public class ExactHashtagPredicate extends ChangeIndexPredicate {
+  public ExactHashtagPredicate(String hashtag) {
     // Use toLowerCase without locale to match behavior in ChangeField.
     // TODO(dborowitz): Change both.
     super(ChangeField.HASHTAG, HashtagsUtil.cleanupHashtag(hashtag).toLowerCase());
   }
 
   @Override
-  public boolean match(ChangeData object) {
-    for (String hashtag : object.notes().load().getHashtags()) {
+  public boolean match(ChangeData cd) {
+    if (Strings.isNullOrEmpty(getValue())) {
+      return cd.hashtags().isEmpty();
+    }
+    for (String hashtag : cd.hashtags()) {
       if (hashtag.equalsIgnoreCase(getValue())) {
         return true;
       }
diff --git a/java/com/google/gerrit/server/query/change/FuzzyHashtagPredicate.java b/java/com/google/gerrit/server/query/change/FuzzyHashtagPredicate.java
new file mode 100644
index 0000000..35c96ef
--- /dev/null
+++ b/java/com/google/gerrit/server/query/change/FuzzyHashtagPredicate.java
@@ -0,0 +1,38 @@
+// Copyright (C) 2021 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.server.query.change;
+
+import static com.google.gerrit.server.index.change.ChangeField.FUZZY_HASHTAG;
+
+import com.google.gerrit.server.index.change.ChangeIndex;
+
+public class FuzzyHashtagPredicate extends ChangeIndexPredicate {
+  protected final ChangeIndex index;
+
+  public FuzzyHashtagPredicate(String hashtag, ChangeIndex index) {
+    super(FUZZY_HASHTAG, hashtag.toLowerCase());
+    this.index = index;
+  }
+
+  @Override
+  public boolean match(ChangeData cd) {
+    return cd.hashtags().stream().anyMatch(ht -> ht.toLowerCase().contains(getValue()));
+  }
+
+  @Override
+  public int getCost() {
+    return 1;
+  }
+}
diff --git a/java/com/google/gerrit/server/query/change/RegexHashtagPredicate.java b/java/com/google/gerrit/server/query/change/RegexHashtagPredicate.java
new file mode 100644
index 0000000..24efa6a
--- /dev/null
+++ b/java/com/google/gerrit/server/query/change/RegexHashtagPredicate.java
@@ -0,0 +1,51 @@
+// Copyright (C) 2021 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.server.query.change;
+
+import static com.google.gerrit.server.index.change.ChangeField.HASHTAG;
+
+import dk.brics.automaton.RegExp;
+import dk.brics.automaton.RunAutomaton;
+
+public class RegexHashtagPredicate extends ChangeRegexPredicate {
+  protected final RunAutomaton pattern;
+
+  public RegexHashtagPredicate(String re) {
+    super(HASHTAG, re);
+
+    if (re.startsWith("^")) {
+      re = re.substring(1);
+    }
+
+    if (re.endsWith("$") && !re.endsWith("\\$")) {
+      re = re.substring(0, re.length() - 1);
+    }
+
+    this.pattern = new RunAutomaton(new RegExp(re).toAutomaton());
+  }
+
+  @Override
+  public boolean match(ChangeData cd) {
+    if (cd.hashtags().isEmpty()) {
+      return false;
+    }
+    return cd.hashtags().stream().anyMatch(ht -> pattern.run(ht));
+  }
+
+  @Override
+  public int getCost() {
+    return 1;
+  }
+}
diff --git a/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java b/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
index cbeb59d..de9c0a5 100644
--- a/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
+++ b/javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java
@@ -1951,16 +1951,17 @@
     Change change1 = insert(repo, newChange(repo));
     Change change2 = insert(repo, newChange(repo));
 
-    HashtagsInput in = new HashtagsInput();
-    in.add = ImmutableSet.of("foo");
-    gApi.changes().id(change1.getId().get()).setHashtags(in);
-
-    in.add = ImmutableSet.of("foo", "bar", "a tag", "ACamelCaseTag");
-    gApi.changes().id(change2.getId().get()).setHashtags(in);
-
+    addHashtags(change1.getId(), "foo", "aaa-bbb-ccc");
+    addHashtags(change2.getId(), "foo", "bar", "a tag", "ACamelCaseTag");
     return ImmutableList.of(change1, change2);
   }
 
+  private void addHashtags(Change.Id changeId, String... hashtags) throws Exception {
+    HashtagsInput in = new HashtagsInput();
+    in.add = ImmutableSet.copyOf(hashtags);
+    gApi.changes().id(changeId.get()).setHashtags(in);
+  }
+
   @Test
   public void byHashtag() throws Exception {
     List<Change> changes = setUpHashtagChanges();
@@ -1976,6 +1977,31 @@
   }
 
   @Test
+  public void byHashtagFullText() throws Exception {
+    assume().that(getSchema().hasField(ChangeField.FUZZY_HASHTAG)).isTrue();
+    List<Change> changes = setUpHashtagChanges();
+    assertQuery("inhashtag:foo", changes.get(1), changes.get(0));
+    assertQuery("inhashtag:bbb", changes.get(0));
+    assertQuery("inhashtag:tag", changes.get(1));
+  }
+
+  @Test
+  public void byHashtagRegex() throws Exception {
+    TestRepository<Repo> repo = createProject("repo");
+    Change change1 = insert(repo, newChange(repo));
+    Change change2 = insert(repo, newChange(repo));
+    Change change3 = insert(repo, newChange(repo));
+    addHashtags(change1.getId(), "feature1");
+    addHashtags(change1.getId(), "trending");
+    addHashtags(change2.getId(), "Cherrypick-feature1");
+    addHashtags(change3.getId(), "feature1-fixup");
+
+    assertQuery("inhashtag:^feature1.*", change3, change1);
+    assertQuery("inhashtag:{^.*feature1$}", change2, change1);
+    assertQuery("inhashtag:^trending.*", change1);
+  }
+
+  @Test
   public void byDefault() throws Exception {
     TestRepository<Repo> repo = createProject("repo");