diff --git a/src/main/java/com/googlesource/gerrit/plugins/serviceuser/RegisterServiceUser.java b/src/main/java/com/googlesource/gerrit/plugins/serviceuser/RegisterServiceUser.java
new file mode 100644
index 0000000..f01b56f
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/serviceuser/RegisterServiceUser.java
@@ -0,0 +1,203 @@
+// 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.plugins.serviceuser;
+
+import static com.google.gerrit.server.permissions.GlobalPermission.ADMINISTRATE_SERVER;
+import static com.googlesource.gerrit.plugins.serviceuser.CreateServiceUser.KEY_CREATED_AT;
+import static com.googlesource.gerrit.plugins.serviceuser.CreateServiceUser.KEY_CREATED_BY;
+import static com.googlesource.gerrit.plugins.serviceuser.CreateServiceUser.KEY_CREATOR_ID;
+import static com.googlesource.gerrit.plugins.serviceuser.CreateServiceUser.KEY_OWNER;
+import static com.googlesource.gerrit.plugins.serviceuser.CreateServiceUser.USER;
+
+import com.google.common.base.Function;
+import com.google.common.base.Strings;
+import com.google.common.collect.Lists;
+import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.Project;
+import com.google.gerrit.extensions.annotations.PluginName;
+import com.google.gerrit.extensions.annotations.RequiresCapability;
+import com.google.gerrit.extensions.common.AccountInfo;
+import com.google.gerrit.extensions.restapi.AuthException;
+import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.extensions.restapi.IdString;
+import com.google.gerrit.extensions.restapi.MethodNotAllowedException;
+import com.google.gerrit.extensions.restapi.Response;
+import com.google.gerrit.extensions.restapi.RestApiException;
+import com.google.gerrit.extensions.restapi.RestCollectionCreateView;
+import com.google.gerrit.server.CurrentUser;
+import com.google.gerrit.server.GerritPersonIdent;
+import com.google.gerrit.server.IdentifiedUser;
+import com.google.gerrit.server.account.AccountLoader;
+import com.google.gerrit.server.account.AccountResolver;
+import com.google.gerrit.server.account.AccountResolver.UnresolvableAccountException;
+import com.google.gerrit.server.config.ConfigResource;
+import com.google.gerrit.server.config.PluginConfig;
+import com.google.gerrit.server.config.PluginConfigFactory;
+import com.google.gerrit.server.git.meta.MetaDataUpdate;
+import com.google.gerrit.server.group.GroupResolver;
+import com.google.gerrit.server.permissions.PermissionBackend;
+import com.google.gerrit.server.permissions.PermissionBackendException;
+import com.google.gerrit.server.project.ProjectCache;
+import com.google.gerrit.server.project.ProjectLevelConfig;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import com.google.inject.Singleton;
+import com.googlesource.gerrit.plugins.serviceuser.GetServiceUser.ServiceUserInfo;
+import com.googlesource.gerrit.plugins.serviceuser.RegisterServiceUser.Input;
+import java.io.IOException;
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
+import java.util.Arrays;
+import java.util.Calendar;
+import java.util.Date;
+import java.util.List;
+import java.util.Locale;
+import org.eclipse.jgit.errors.ConfigInvalidException;
+import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.lib.PersonIdent;
+
+@RequiresCapability(CreateServiceUserCapability.ID)
+@Singleton
+class RegisterServiceUser
+    implements RestCollectionCreateView<ConfigResource, ServiceUserResource, Input> {
+
+  static class Input {
+    String username;
+    String creator;
+    String owner;
+  }
+
+  private final AccountResolver accountResolver;
+  private final GroupResolver groupResolver;
+  private final PluginConfig cfg;
+  private final List<String> blockedNames;
+  private final Provider<CurrentUser> userProvider;
+  private final MetaDataUpdate.User metaDataUpdateFactory;
+  private final Project.NameKey allProjects;
+  private final ProjectLevelConfig storage;
+  private final DateFormat rfc2822DateFormatter;
+  private final AccountLoader.Factory accountLoader;
+  private final PermissionBackend permissionBackend;
+
+  @Inject
+  RegisterServiceUser(
+      AccountResolver accountResolver,
+      GroupResolver groupResolver,
+      PluginConfigFactory cfgFactory,
+      @PluginName String pluginName,
+      Provider<CurrentUser> userProvider,
+      @GerritPersonIdent PersonIdent gerritIdent,
+      MetaDataUpdate.User metaDataUpdateFactory,
+      ProjectCache projectCache,
+      AccountLoader.Factory accountLoader,
+      PermissionBackend permissionBackend) {
+    this.accountResolver = accountResolver;
+    this.groupResolver = groupResolver;
+    this.cfg = cfgFactory.getFromGerritConfig(pluginName);
+    this.blockedNames =
+        Lists.transform(
+            Arrays.asList(cfg.getStringList("block")),
+            new Function<String, String>() {
+              @Override
+              public String apply(String blockedName) {
+                return blockedName.toLowerCase();
+              }
+            });
+    this.userProvider = userProvider;
+    this.metaDataUpdateFactory = metaDataUpdateFactory;
+    this.storage = projectCache.getAllProjects().getConfig(pluginName + ".db");
+    this.allProjects = projectCache.getAllProjects().getProject().getNameKey();
+    this.rfc2822DateFormatter = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss Z", Locale.US);
+    this.rfc2822DateFormatter.setCalendar(
+        Calendar.getInstance(gerritIdent.getTimeZone(), Locale.US));
+    this.accountLoader = accountLoader;
+    this.permissionBackend = permissionBackend;
+  }
+
+  @Override
+  public Response<ServiceUserInfo> apply(ConfigResource parentResource, IdString id, Input input)
+      throws RestApiException, IOException, ConfigInvalidException, PermissionBackendException {
+    CurrentUser requestingUser = userProvider.get();
+    if (requestingUser == null || !requestingUser.isIdentifiedUser()) {
+      throw new AuthException("authentication required");
+    }
+
+    if (input == null) {
+      input = new Input();
+    }
+
+    IdentifiedUser user;
+    try {
+      user = accountResolver.resolve(input.username).asUniqueUser();
+    } catch (UnresolvableAccountException e) {
+      throw new BadRequestException("Username does not exist");
+    }
+
+    if (!requestingUser.getAccountId().equals(user.getAccountId())
+        && !permissionBackend.user(requestingUser).testOrFalse(ADMINISTRATE_SERVER)) {
+      throw new MethodNotAllowedException("Forbidden");
+    }
+
+    Config db = storage.get();
+    if (db.getSubsections(USER).contains(input.username)) {
+      return Response.none();
+    }
+
+    if (blockedNames.contains(input.username.toLowerCase())) {
+      throw new BadRequestException(
+          "The username '" + input.username + "' is not allowed as name for service users.");
+    }
+
+    String creator;
+    Account.Id creatorId;
+    if (Strings.isNullOrEmpty(input.creator)) {
+      creator = requestingUser.getUserName().orElse(null);
+      creatorId = requestingUser.asIdentifiedUser().getAccountId();
+    } else {
+      creator = input.creator;
+      creatorId = accountResolver.resolve(input.creator).asUniqueUser().getAccountId();
+    }
+    String creationDate = rfc2822DateFormatter.format(new Date());
+
+    String owner = null;
+    if (!Strings.isNullOrEmpty(input.owner)) {
+      try {
+        owner = groupResolver.parse(input.owner).getGroupUUID().toString();
+      } catch (UnresolvableAccountException e) {
+        throw new BadRequestException("The group '" + input.owner + "' does not exist");
+      }
+    }
+
+    db.setInt(USER, input.username, KEY_CREATOR_ID, creatorId.get());
+    if (creator != null) {
+      db.setString(USER, input.username, KEY_CREATED_BY, creator);
+    }
+    if (owner != null) {
+      db.setString(USER, input.username, KEY_OWNER, owner);
+    }
+    db.setString(USER, input.username, KEY_CREATED_AT, creationDate);
+
+    MetaDataUpdate md = metaDataUpdateFactory.create(allProjects);
+    md.setMessage("Create service user '" + input.username + "'\n");
+    storage.commit(md);
+
+    ServiceUserInfo info = new ServiceUserInfo(new AccountInfo(user.getAccountId().get()));
+    AccountLoader al = accountLoader.create(true);
+    info.createdBy = al.get(creatorId);
+    al.fill();
+    info.createdAt = creationDate;
+    return Response.created(info);
+  }
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/serviceuser/RegisterServiceUserCommand.java b/src/main/java/com/googlesource/gerrit/plugins/serviceuser/RegisterServiceUserCommand.java
new file mode 100644
index 0000000..fb8503c
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/serviceuser/RegisterServiceUserCommand.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.plugins.serviceuser;
+
+import com.google.gerrit.extensions.annotations.RequiresCapability;
+import com.google.gerrit.extensions.restapi.IdString;
+import com.google.gerrit.extensions.restapi.RestApiException;
+import com.google.gerrit.server.config.ConfigResource;
+import com.google.gerrit.server.permissions.PermissionBackendException;
+import com.google.gerrit.sshd.CommandMetaData;
+import com.google.gerrit.sshd.SshCommand;
+import com.google.inject.Inject;
+import java.io.IOException;
+import org.eclipse.jgit.errors.ConfigInvalidException;
+import org.kohsuke.args4j.Argument;
+import org.kohsuke.args4j.Option;
+
+@RequiresCapability(CreateServiceUserCapability.ID)
+@CommandMetaData(name = "register", description = "Register Service User")
+class RegisterServiceUserCommand extends SshCommand {
+
+  @Argument(index = 0, required = true, metaVar = "USERNAME", usage = "name of the service user")
+  private String username;
+
+  @Option(
+      name = "--creator",
+      required = false,
+      metaVar = "CREATOR",
+      usage = "name of the creator of the service user")
+  private String creator;
+
+  @Option(
+      name = "--owner",
+      required = false,
+      metaVar = "OWNER",
+      usage = "group that owns the service user")
+  private String owner;
+
+  @Inject private RegisterServiceUser registerServiceUser;
+
+  @Override
+  protected void run()
+      throws IOException, UnloggedFailure, ConfigInvalidException, PermissionBackendException {
+    RegisterServiceUser.Input input = new RegisterServiceUser.Input();
+    input.username = username;
+    input.creator = creator;
+    input.owner = owner;
+
+    try {
+      registerServiceUser.apply(new ConfigResource(), IdString.fromDecoded(username), input);
+    } catch (RestApiException e) {
+      throw die(e.getMessage());
+    }
+  }
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/serviceuser/SshModule.java b/src/main/java/com/googlesource/gerrit/plugins/serviceuser/SshModule.java
index f775e4c..40a1509 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/serviceuser/SshModule.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/serviceuser/SshModule.java
@@ -21,5 +21,6 @@
   @Override
   protected void configureCommands() {
     command(CreateServiceUserCommand.class);
+    command(RegisterServiceUserCommand.class);
   }
 }
diff --git a/src/main/resources/Documentation/cmd-register.md b/src/main/resources/Documentation/cmd-register.md
new file mode 100644
index 0000000..3378a2c
--- /dev/null
+++ b/src/main/resources/Documentation/cmd-register.md
@@ -0,0 +1,50 @@
+@PLUGIN@ register
+=================
+
+NAME
+----
+@PLUGIN@ register - Registers an existing user as a service user
+
+SYNOPSIS
+--------
+```
+ssh -p @SSH_PORT@ @SSH_HOST@ @PLUGIN@ register
+  --creator <CREATOR>
+  --owner <OWNER>
+  <USERNAME>
+```
+
+DESCRIPTION
+-----------
+Registers an existing user as a service user.
+
+ACCESS
+------
+Caller must be a member of a group that is granted the
+'Create Service User' capability (provided by this plugin) or the
+'Administrate Server' capability. If not possessing the 'Administrate
+Server' capability, the user to be registered as a service user must
+also be the caller.
+
+SCRIPTING
+---------
+This command is intended to be used in scripts.
+
+OPTIONS
+-------
+
+`--creator`
+:   Username of the user that will be set as the creator of the
+    serviceuser. Defaults to the caller.
+
+`--owner`
+:   ID or name of the group that will own the service user. Defaults
+    to no owner group being set.
+
+EXAMPLES
+--------
+Register a service user:
+
+```
+  $ ssh -p @SSH_PORT@ @SSH_HOST@ @PLUGIN@ register --creator admin --owner Administrators username
+```