diff --git a/owners-api/BUILD b/owners-api/BUILD
new file mode 100644
index 0000000..ccf66e6
--- /dev/null
+++ b/owners-api/BUILD
@@ -0,0 +1,36 @@
+load("//tools/bzl:junit.bzl", "junit_tests")
+load("//tools/bzl:plugin.bzl", "PLUGIN_DEPS", "PLUGIN_DEPS_NEVERLINK", "PLUGIN_TEST_DEPS", "gerrit_plugin")
+
+gerrit_plugin(
+    name = "owners-api",
+    srcs = glob([
+        "src/main/java/**/*.java",
+    ]),
+    dir_name = "owners",
+    manifest_entries = [
+        "Implementation-Title: Gerrit OWNERS api plugin",
+        "Implementation-URL: https://gerrit.googlesource.com/plugins/owners",
+        "Gerrit-PluginName: owners-api",
+        "Gerrit-Module: com.googlesource.gerrit.owners.common.AutoassignModule",
+    ],
+    resources = glob(["src/main/**/*"]),
+    deps = [],
+)
+
+java_library(
+    name = "owners-api_deps",
+    srcs = glob([
+        "src/main/java/**/*.java",
+    ]),
+    visibility = ["//visibility:public"],
+    deps = PLUGIN_DEPS_NEVERLINK,
+)
+
+junit_tests(
+    name = "owners_api_tests",
+    testonly = 1,
+    srcs = glob(["src/test/java/**/*.java"]),
+    deps = PLUGIN_DEPS + PLUGIN_TEST_DEPS + [
+        ":owners-api_deps",
+    ],
+)
diff --git a/owners-api/src/main/java/com/googlesource/gerrit/owners/api/OwnersApiModule.java b/owners-api/src/main/java/com/googlesource/gerrit/owners/api/OwnersApiModule.java
new file mode 100644
index 0000000..54ee51d
--- /dev/null
+++ b/owners-api/src/main/java/com/googlesource/gerrit/owners/api/OwnersApiModule.java
@@ -0,0 +1,27 @@
+// 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.googlesource.gerrit.owners.api;
+
+import com.google.gerrit.extensions.registration.DynamicItem;
+import com.google.inject.AbstractModule;
+
+public class OwnersApiModule extends AbstractModule {
+
+  @Override
+  protected void configure() {
+    DynamicItem.itemOf(binder(), OwnersAttentionSet.class);
+  }
+}
diff --git a/owners-api/src/main/java/com/googlesource/gerrit/owners/api/OwnersAttentionSet.java b/owners-api/src/main/java/com/googlesource/gerrit/owners/api/OwnersAttentionSet.java
new file mode 100644
index 0000000..31cd2a4
--- /dev/null
+++ b/owners-api/src/main/java/com/googlesource/gerrit/owners/api/OwnersAttentionSet.java
@@ -0,0 +1,33 @@
+// 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.googlesource.gerrit.owners.api;
+
+import com.google.gerrit.entities.Account;
+import com.google.gerrit.extensions.common.ChangeInfo;
+import java.util.Collection;
+
+/** API to expose a mechanism to selectively add owners to the attention-set. */
+public interface OwnersAttentionSet {
+
+  /**
+   * Select the owners that should be added to the attention-set.
+   *
+   * @param changeInfo change under review
+   * @param owners set of owners associated with a change.
+   * @return subset of owners that need to be added to the attention-set.
+   */
+  Collection<Account.Id> addToAttentionSet(ChangeInfo changeInfo, Collection<Account.Id> owners);
+}
diff --git a/owners-api/src/test/java/com/googlesource/gerrit/owners/api/OwnersAttentionSetIT.java b/owners-api/src/test/java/com/googlesource/gerrit/owners/api/OwnersAttentionSetIT.java
new file mode 100644
index 0000000..8a3ec18
--- /dev/null
+++ b/owners-api/src/test/java/com/googlesource/gerrit/owners/api/OwnersAttentionSetIT.java
@@ -0,0 +1,67 @@
+// 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.googlesource.gerrit.owners.api;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.gerrit.acceptance.LightweightPluginDaemonTest;
+import com.google.gerrit.acceptance.TestPlugin;
+import com.google.gerrit.entities.Account.Id;
+import com.google.gerrit.extensions.common.ChangeInfo;
+import com.google.gerrit.extensions.registration.DynamicItem;
+import com.google.inject.AbstractModule;
+import com.google.inject.Inject;
+import com.google.inject.Module;
+import com.google.inject.Scopes;
+import java.util.Collection;
+import org.junit.Test;
+
+@TestPlugin(
+    name = "owners-api",
+    sysModule = "com.googlesource.gerrit.owners.api.OwnersAttentionSetIT$TestModule")
+public class OwnersAttentionSetIT extends LightweightPluginDaemonTest {
+
+  @Inject private DynamicItem<OwnersAttentionSet> ownerAttentionSetItem;
+
+  @Override
+  public Module createModule() {
+    return new OwnersApiModule();
+  }
+
+  public static class TestModule extends AbstractModule {
+    @Override
+    protected void configure() {
+      DynamicItem.bind(binder(), OwnersAttentionSet.class)
+          .to(SelectFirstOwnerForAttentionSet.class)
+          .in(Scopes.SINGLETON);
+    }
+  }
+
+  public static class SelectFirstOwnerForAttentionSet implements OwnersAttentionSet {
+    @Override
+    public Collection<Id> addToAttentionSet(ChangeInfo changeInfo, Collection<Id> owners) {
+      return null;
+    }
+  }
+
+  @Test
+  public void shouldAllowOwnersAttentionSetOverride() {
+    OwnersAttentionSet attentionSetSelector = ownerAttentionSetItem.get();
+
+    assertThat(attentionSetSelector).isNotNull();
+    assertThat(attentionSetSelector.getClass()).isEqualTo(SelectFirstOwnerForAttentionSet.class);
+  }
+}
diff --git a/owners-autoassign/BUILD b/owners-autoassign/BUILD
index 463afcb..024be42 100644
--- a/owners-autoassign/BUILD
+++ b/owners-autoassign/BUILD
@@ -12,11 +12,11 @@
         "Implementation-URL: https://gerrit.googlesource.com/plugins/owners",
         "Gerrit-PluginName: owners-autoassign",
         "Gerrit-Module: com.googlesource.gerrit.owners.common.AutoassignModule",
-        "Gerrit-ApiVersion: 2.16",
     ],
     resources = glob(["src/main/**/*"]),
     deps = [
         "//owners-common",
+        "//plugins/owners-api",
     ],
 )
 
@@ -28,6 +28,7 @@
     visibility = ["//visibility:public"],
     deps = PLUGIN_DEPS_NEVERLINK + [
         "//owners-common",
+        "//plugins/owners-api",
     ],
 )
 
@@ -37,6 +38,7 @@
     srcs = glob(["src/test/java/**/*.java"]),
     deps = PLUGIN_DEPS + PLUGIN_TEST_DEPS + [
         "//owners-common",
+        "//plugins/owners-api",
         ":owners-autoassign_deps",
     ],
 )
diff --git a/owners-autoassign/src/main/java/com/googlesource/gerrit/owners/common/ReviewerManager.java b/owners-autoassign/src/main/java/com/googlesource/gerrit/owners/common/ReviewerManager.java
index c3708b5..eef9321 100644
--- a/owners-autoassign/src/main/java/com/googlesource/gerrit/owners/common/ReviewerManager.java
+++ b/owners-autoassign/src/main/java/com/googlesource/gerrit/owners/common/ReviewerManager.java
@@ -21,9 +21,11 @@
 import com.google.gerrit.entities.Project;
 import com.google.gerrit.extensions.api.GerritApi;
 import com.google.gerrit.extensions.api.changes.AddReviewerInput;
+import com.google.gerrit.extensions.api.changes.AttentionSetInput;
 import com.google.gerrit.extensions.api.changes.ChangeApi;
 import com.google.gerrit.extensions.api.changes.ReviewInput;
 import com.google.gerrit.extensions.common.ChangeInfo;
+import com.google.gerrit.extensions.registration.DynamicItem;
 import com.google.gerrit.extensions.restapi.RestApiException;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.permissions.ChangePermission;
@@ -33,8 +35,12 @@
 import com.google.gerrit.server.util.OneOffRequestContext;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
+import com.googlesource.gerrit.owners.api.OwnersAttentionSet;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.stream.Collectors;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -48,6 +54,16 @@
   private final ChangeData.Factory changeDataFactory;
   private final PermissionBackend permissionBackend;
 
+  /**
+   * TODO: The optional injection here is needed for keeping backward compatibility with existing
+   * setups that do not have the owners-api.jar configured as Gerrit libModule.
+   *
+   * <p>Once merged to master, the optional injection can go and this can be moved as extra argument
+   * in the constructor.
+   */
+  @Inject(optional = true)
+  private DynamicItem<OwnersAttentionSet> ownersForAttentionSet;
+
   @Inject
   public ReviewerManager(
       OneOffRequestContext requestContext,
@@ -71,6 +87,12 @@
         // TODO(davido): Switch back to using changes API again,
         // when it supports batch mode for adding reviewers
         ReviewInput in = new ReviewInput();
+        Collection<Account.Id> reviewersAccounts =
+            Optional.ofNullable(ownersForAttentionSet)
+                .map(DynamicItem::get)
+                .filter(Objects::nonNull)
+                .map(owners -> owners.addToAttentionSet(changeInfo, reviewers))
+                .orElse(reviewers);
         in.reviewers = new ArrayList<>(reviewers.size());
         for (Account.Id account : reviewers) {
           if (isVisibleTo(changeInfo, account)) {
@@ -84,6 +106,16 @@
                 changeInfo._number);
           }
         }
+
+        in.ignoreAutomaticAttentionSetRules = true;
+        in.addToAttentionSet =
+            reviewersAccounts.stream()
+                .map(
+                    (reviewer) ->
+                        new AttentionSetInput(
+                            reviewer.toString(), "Selected as member of the OWNERS file"))
+                .collect(Collectors.toList());
+
         gApi.changes().id(changeInfo.id).current().review(in);
       }
     } catch (RestApiException e) {
diff --git a/owners-autoassign/src/main/resources/Documentation/attention-set.md b/owners-autoassign/src/main/resources/Documentation/attention-set.md
new file mode 100644
index 0000000..7ad9a55
--- /dev/null
+++ b/owners-autoassign/src/main/resources/Documentation/attention-set.md
@@ -0,0 +1,88 @@
+## Attention-Set
+
+The owners-autoassign plugin allows to customize the selection of owners
+that need to be added to the attention-set.
+By default, Gerrit adds all reviewers to the attention-set, which could
+not be ideal when the list of owners automatically assigned could be
+quite long, due to the hierarchy of the OWNERS files in the parent
+directories.
+
+The `owners-api.jar` libModule included in the owners' plugin project contains
+a generic interface that can be used to customize Gerrit's default
+attention-set behaviour.
+
+## owner-api setup
+
+Copy the `owners-api.jar` libModule into the $GERRIT_SITE/lib directory
+and add the following entry to `gerrit.config`:
+
+```
+[gerrit]
+  installModule = com.googlesource.gerrit.owners.api.OwnersApiModule
+```
+
+## Customization of the attention-set selection
+
+The OwnersAttentionSet API, contained in the owners-api.jar libModule,
+provides the following interface:
+
+```
+public interface OwnersAttentionSet {
+
+  Collection<Account.Id> addToAttentionSet(ChangeInfo changeInfo, Collection<Account.Id> owners);
+}
+```
+
+Any other plugin, or script, can implement the interface and provide
+an alternative implementation of the Gerrit's default mechanism.
+
+Example: select two random owners and add to the attention set by adding the
+following script as $GERRIT_SITE/plugins/owners-attentionset-1.0.groovy.
+
+```
+import com.google.inject.*
+import com.google.gerrit.common.*
+import com.google.gerrit.entities.*
+import com.google.gerrit.extensions.common.*
+import com.google.gerrit.extensions.registration.*
+import com.googlesource.gerrit.owners.api.*
+import java.util.*
+
+@Singleton
+class MyAttentionSet implements OwnersAttentionSet {
+  def desiredAttentionSet = 3
+
+  Collection<Account.Id> addToAttentionSet(ChangeInfo changeInfo, Collection<Account.Id> owners) {
+    def currentAttentionSet = changeInfo.attentionSet.size()
+
+    // There is already the desired number of attention-set
+    if (currentAttentionSet >= desiredAttentionSet) {
+      return Collections.emptyList()
+    }
+
+    // All owners are within the attention-set limits
+    if (owners.size() <= desiredAttentionSet) {
+      return owners
+    }
+
+    // Select randomly some owners for the attention-set
+    def shuffledOwners = owners.asType(List)
+    Collections.shuffle shuffledOwners
+    return shuffledOwners.subList(0,desiredAttentionSet)
+  }
+}
+
+class MyAttentionSetModule extends AbstractModule {
+
+  protected void configure() {
+    DynamicItem.bind(binder(), OwnersAttentionSet.class)
+        .to(MyAttentionSet.class)
+        .in(Scopes.SINGLETON)
+  }
+}
+
+modules = [ MyAttentionSetModule.class ]
+```
+
+**NOTE**: Install the [groovy-provider plugin](https://gerrit.googlesource.com/plugins/scripting/groovy-provider/)
+for enabling Gerrit to load Groovy scripts as plugins.
\ No newline at end of file
diff --git a/owners-autoassign/src/test/java/com/googlesource/gerrit/owners/common/OwnersAutoassignIT.java b/owners-autoassign/src/test/java/com/googlesource/gerrit/owners/common/OwnersAutoassignIT.java
new file mode 100644
index 0000000..374657c
--- /dev/null
+++ b/owners-autoassign/src/test/java/com/googlesource/gerrit/owners/common/OwnersAutoassignIT.java
@@ -0,0 +1,64 @@
+// 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.googlesource.gerrit.owners.common;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.gerrit.acceptance.LightweightPluginDaemonTest;
+import com.google.gerrit.acceptance.TestPlugin;
+import com.google.gerrit.acceptance.UseLocalDisk;
+import com.google.gerrit.extensions.api.changes.ChangeApi;
+import com.google.gerrit.extensions.client.ReviewerState;
+import com.google.gerrit.extensions.common.AccountInfo;
+import com.google.inject.AbstractModule;
+import java.util.Collection;
+import org.junit.Test;
+
+@TestPlugin(
+    name = "owners-api",
+    sysModule = "com.googlesource.gerrit.owners.common.OwnersAutoassignIT$TestModule")
+public class OwnersAutoassignIT extends LightweightPluginDaemonTest {
+
+  public static class TestModule extends AbstractModule {
+    @Override
+    protected void configure() {
+      install(new AutoassignModule());
+    }
+  }
+
+  @UseLocalDisk
+  @Test
+  public void shouldAutoassignOneOwner() throws Exception {
+    String ownerEmail = user.email();
+
+    pushFactory
+        .create(
+            admin.newIdent(),
+            testRepo,
+            "Set OWNERS",
+            "OWNERS",
+            "inherited: false\n" + "owners:\n" + "- " + ownerEmail)
+        .to("refs/heads/master")
+        .assertOkStatus();
+
+    ChangeApi changeApi = change(createChange());
+    Collection<AccountInfo> reviewers = changeApi.get().reviewers.get(ReviewerState.REVIEWER);
+
+    assertThat(reviewers).hasSize(1);
+    AccountInfo reviewer = reviewers.iterator().next();
+    assertThat(reviewer.email).isEqualTo(ownerEmail);
+  }
+}
diff --git a/owners-autoassign/src/test/java/com/googlesource/gerrit/owners/common/OwnersAutoassignWithAttentionSetIT.java b/owners-autoassign/src/test/java/com/googlesource/gerrit/owners/common/OwnersAutoassignWithAttentionSetIT.java
new file mode 100644
index 0000000..5495240
--- /dev/null
+++ b/owners-autoassign/src/test/java/com/googlesource/gerrit/owners/common/OwnersAutoassignWithAttentionSetIT.java
@@ -0,0 +1,93 @@
+// 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.googlesource.gerrit.owners.common;
+
+import static com.google.common.truth.Truth.assertThat;
+import static java.util.stream.Collectors.toList;
+
+import com.google.gerrit.acceptance.LightweightPluginDaemonTest;
+import com.google.gerrit.acceptance.TestPlugin;
+import com.google.gerrit.acceptance.UseLocalDisk;
+import com.google.gerrit.entities.Account.Id;
+import com.google.gerrit.extensions.client.ReviewerState;
+import com.google.gerrit.extensions.common.ChangeInfo;
+import com.google.gerrit.extensions.registration.DynamicItem;
+import com.google.inject.AbstractModule;
+import com.google.inject.Module;
+import com.google.inject.Scopes;
+import com.googlesource.gerrit.owners.api.OwnersApiModule;
+import com.googlesource.gerrit.owners.api.OwnersAttentionSet;
+import java.util.Collection;
+import org.junit.Test;
+
+@TestPlugin(
+    name = "owners-autoassign",
+    sysModule =
+        "com.googlesource.gerrit.owners.common.OwnersAutoassignWithAttentionSetIT$TestModule")
+public class OwnersAutoassignWithAttentionSetIT extends LightweightPluginDaemonTest {
+
+  @Override
+  public Module createModule() {
+    return new OwnersApiModule();
+  }
+
+  public static class TestModule extends AbstractModule {
+    @Override
+    protected void configure() {
+      install(new AutoassignModule());
+
+      DynamicItem.bind(binder(), OwnersAttentionSet.class)
+          .to(SelectFirstOwnerForAttentionSet.class)
+          .in(Scopes.SINGLETON);
+    }
+  }
+
+  public static class SelectFirstOwnerForAttentionSet implements OwnersAttentionSet {
+
+    @Override
+    public Collection<Id> addToAttentionSet(ChangeInfo changeInfo, Collection<Id> owners) {
+      return owners.stream().limit(1).collect(toList());
+    }
+  }
+
+  @UseLocalDisk
+  @Test
+  public void shouldAutoassignTwoOwnersWithOneAttentionSet() throws Exception {
+    String ownerEmail1 = user.email();
+    String ownerEmail2 = accountCreator.user2().email();
+
+    pushFactory
+        .create(
+            admin.newIdent(),
+            testRepo,
+            "Set OWNERS",
+            "OWNERS",
+            "inherited: false\n"
+                + "owners:\n"
+                + "- "
+                + ownerEmail1
+                + "\n"
+                + "- "
+                + ownerEmail2
+                + "\n")
+        .to("refs/heads/master")
+        .assertOkStatus();
+
+    ChangeInfo change = change(createChange()).get();
+    assertThat(change.reviewers.get(ReviewerState.REVIEWER)).hasSize(2);
+    assertThat(change.attentionSet).hasSize(1);
+  }
+}
diff --git a/owners/BUILD b/owners/BUILD
index 3acc05b..ab6705e 100644
--- a/owners/BUILD
+++ b/owners/BUILD
@@ -36,7 +36,6 @@
         "Implementation-URL: https://gerrit.googlesource.com/plugins/owners",
         "Gerrit-PluginName: owners",
         "Gerrit-Module: com.googlesource.gerrit.owners.OwnersModule",
-        "Gerrit-ApiVersion: 2.16",
     ],
     resources = glob(["src/main/resources/**/*"]),
     deps = [