diff --git a/core/api/system-current.txt b/core/api/system-current.txt
index 802e61403fc39..8887686d5d40b 100644
--- a/core/api/system-current.txt
+++ b/core/api/system-current.txt
@@ -10042,6 +10042,7 @@ package android.os {
     method @NonNull @RequiresPermission(anyOf={android.Manifest.permission.MANAGE_USERS, android.Manifest.permission.CREATE_USERS}) public android.os.NewUserResponse createUser(@NonNull android.os.NewUserRequest);
     method @NonNull public java.util.List<android.os.UserHandle> getAllProfiles();
     method @NonNull public java.util.List<android.os.UserHandle> getEnabledProfiles();
+    method @Nullable @RequiresPermission(anyOf={android.Manifest.permission.MANAGE_USERS, android.Manifest.permission.CREATE_USERS, android.Manifest.permission.QUERY_USERS}) public android.os.UserHandle getMainUser();
     method @Nullable @RequiresPermission(anyOf={android.Manifest.permission.MANAGE_USERS, android.Manifest.permission.INTERACT_ACROSS_USERS}) public android.os.UserHandle getProfileParent(@NonNull android.os.UserHandle);
     method @RequiresPermission(anyOf={android.Manifest.permission.MANAGE_USERS, android.Manifest.permission.CREATE_USERS, android.Manifest.permission.QUERY_USERS}) public int getRemainingCreatableProfileCount(@NonNull String);
     method @RequiresPermission(anyOf={android.Manifest.permission.MANAGE_USERS, android.Manifest.permission.CREATE_USERS, android.Manifest.permission.QUERY_USERS}) public int getRemainingCreatableUserCount(@NonNull String);
diff --git a/core/java/android/os/IUserManager.aidl b/core/java/android/os/IUserManager.aidl
index a887f2a6ef29d..eae7ce06008c7 100644
--- a/core/java/android/os/IUserManager.aidl
+++ b/core/java/android/os/IUserManager.aidl
@@ -58,6 +58,7 @@ interface IUserManager {
     void setUserIcon(int userId, in Bitmap icon);
     ParcelFileDescriptor getUserIcon(int userId);
     UserInfo getPrimaryUser();
+    int getMainUserId();
     List<UserInfo> getUsers(boolean excludePartial, boolean excludeDying, boolean excludePreCreated);
     List<UserInfo> getProfiles(int userId, boolean enabledOnly);
     int[] getProfileIds(int userId, boolean enabledOnly);
diff --git a/core/java/android/os/UserManager.java b/core/java/android/os/UserManager.java
index 1f21bfe6cd729..954d1fca4ce07 100644
--- a/core/java/android/os/UserManager.java
+++ b/core/java/android/os/UserManager.java
@@ -2377,14 +2377,16 @@ public class UserManager {
     }
 
     /**
-     * Returns true if the context user is the designated "main user" of the device. This user may
-     * have access to certain features which are limited to at most one user.
+     * Returns {@code true} if the context user is the designated "main user" of the device. This
+     * user may have access to certain features which are limited to at most one user. There will
+     * never be more than one main user on a device.
      *
-     * <p>Currently, the first human user on the device will be the main user; in the future, the
-     * concept may be transferable, so a different user (or even no user at all) may be designated
-     * the main user instead.
+     * <p>Currently, on most form factors the first human user on the device will be the main user;
+     * in the future, the concept may be transferable, so a different user (or even no user at all)
+     * may be designated the main user instead. On other form factors there might not be a main
+     * user.
      *
-     * <p>Note that this will be the not be the system user on devices for which
+     * <p>Note that this will not be the system user on devices for which
      * {@link #isHeadlessSystemUserMode()} returns true.
      * @hide
      */
@@ -2399,6 +2401,29 @@ public class UserManager {
         return user != null && user.isMain();
     }
 
+    /**
+     * Returns the designated "main user" of the device, or {@code null} if there is no main user.
+     *
+     * @see #isMainUser()
+     * @hide
+     */
+    @SystemApi
+    @RequiresPermission(anyOf = {
+            Manifest.permission.MANAGE_USERS,
+            Manifest.permission.CREATE_USERS,
+            Manifest.permission.QUERY_USERS})
+    public @Nullable UserHandle getMainUser() {
+        try {
+            final int mainUserId = mService.getMainUserId();
+            if (mainUserId == UserHandle.USER_NULL) {
+                return null;
+            }
+            return UserHandle.of(mainUserId);
+        } catch (RemoteException re) {
+            throw re.rethrowFromSystemServer();
+        }
+    }
+
     /**
      * Used to check if the context user is an admin user. An admin user is allowed to
      * modify or configure certain settings that aren't available to non-admin users,
diff --git a/services/core/java/com/android/server/pm/UserManagerInternal.java b/services/core/java/com/android/server/pm/UserManagerInternal.java
index 1027f4c031277..df132a97418a0 100644
--- a/services/core/java/com/android/server/pm/UserManagerInternal.java
+++ b/services/core/java/com/android/server/pm/UserManagerInternal.java
@@ -441,4 +441,12 @@ public abstract class UserManagerInternal {
     /** Return the integer types of the given user IDs. Only used for reporting metrics to statsd.
      */
     public abstract int[] getUserTypesForStatsd(@UserIdInt int[] userIds);
+
+    /**
+     * Returns the user id of the main user, or {@link android.os.UserHandle#USER_NULL} if there is
+     * no main user.
+     *
+     * @see UserManager#isMainUser()
+     */
+    public abstract @UserIdInt int getMainUserId();
 }
diff --git a/services/core/java/com/android/server/pm/UserManagerService.java b/services/core/java/com/android/server/pm/UserManagerService.java
index 88e12fa9a6045..c8dffedfd1419 100644
--- a/services/core/java/com/android/server/pm/UserManagerService.java
+++ b/services/core/java/com/android/server/pm/UserManagerService.java
@@ -901,6 +901,25 @@ public class UserManagerService extends IUserManager.Stub {
         return null;
     }
 
+    @Override
+    public @UserIdInt int getMainUserId() {
+        checkQueryOrCreateUsersPermission("get main user id");
+        return getMainUserIdUnchecked();
+    }
+
+    private @UserIdInt int getMainUserIdUnchecked() {
+        synchronized (mUsersLock) {
+            final int userSize = mUsers.size();
+            for (int i = 0; i < userSize; i++) {
+                final UserInfo user = mUsers.valueAt(i).info;
+                if (user.isMain() && !mRemovingUserIds.get(user.id)) {
+                    return user.id;
+                }
+            }
+        }
+        return UserHandle.USER_NULL;
+    }
+
     public @NonNull List<UserInfo> getUsers(boolean excludeDying) {
         return getUsers(/*excludePartial= */ true, excludeDying, /* excludePreCreated= */
                 true);
@@ -6898,6 +6917,12 @@ public class UserManagerService extends IUserManager.Stub {
             }
             return userTypes;
         }
+
+        @Override
+        public @UserIdInt int getMainUserId() {
+            return getMainUserIdUnchecked();
+        }
+
     } // class LocalService