diff --git a/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php b/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
index c7fd96603f7..eed24215eaa 100644
--- a/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
+++ b/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
@@ -4,6 +4,7 @@ namespace Drupal\Core\Installer\Form;
 
 use Drupal\Core\Datetime\TimeZoneFormHelper;
 use Drupal\Core\DependencyInjection\DeprecatedServicePropertyTrait;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
 use Drupal\Core\Extension\ModuleInstallerInterface;
 use Drupal\Core\Form\ConfigFormBase;
 use Drupal\Core\Form\FormStateInterface;
@@ -67,29 +68,39 @@ class SiteConfigureForm extends ConfigFormBase {
    *   The app root.
    * @param string $site_path
    *   The site path.
-   * @param \Drupal\user\UserStorageInterface $user_storage
-   *   The user storage.
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface|\Drupal\user\UserStorageInterface $entityTypeManager
+   *   The entity type manager.
    * @param \Drupal\Core\Extension\ModuleInstallerInterface $module_installer
    *   The module installer.
    * @param \Drupal\Core\Locale\CountryManagerInterface|\Drupal\user\UserNameValidator $userNameValidator
    *   The user validator.
+   * @param bool|null $superUserAccessPolicy
+   *   The value of the 'security.enable_super_user' container parameter.
    */
   public function __construct(
     $root,
     $site_path,
-    UserStorageInterface $user_storage,
+    protected EntityTypeManagerInterface|UserStorageInterface $entityTypeManager,
     ModuleInstallerInterface $module_installer,
     protected CountryManagerInterface|UserNameValidator $userNameValidator,
+    protected ?bool $superUserAccessPolicy = NULL,
   ) {
     $this->root = $root;
     $this->sitePath = $site_path;
-    $this->userStorage = $user_storage;
+    if ($this->entityTypeManager instanceof UserStorageInterface) {
+      @trigger_error('Calling ' . __METHOD__ . '() with the $entityTypeManager argument as UserStorageInterface is deprecated in drupal:10.3.0 and must be EntityTypeManagerInterface in drupal:11.0.0. See https://www.drupal.org/node/3443172', E_USER_DEPRECATED);
+      $this->entityTypeManager = \Drupal::entityTypeManager();
+    }
+    $this->userStorage = $this->entityTypeManager->getStorage('user');
     $this->moduleInstaller = $module_installer;
     if ($userNameValidator instanceof CountryManagerInterface) {
       @trigger_error('Calling ' . __METHOD__ . '() with the $userNameValidator argument as CountryManagerInterface is deprecated in drupal:10.3.0 and must be UserNameValidator in drupal:11.0.0. See https://www.drupal.org/node/3431205', E_USER_DEPRECATED);
-      $userNameValidator = \Drupal::service('user.name_validator');
+      $this->userNameValidator = \Drupal::service('user.name_validator');
+    }
+    if ($this->superUserAccessPolicy === NULL) {
+      @trigger_error('Calling ' . __METHOD__ . '() without the $superUserAccessPolicy argument is deprecated in drupal:10.3.0 and must be passed in drupal:11.0.0. See https://www.drupal.org/node/3443172', E_USER_DEPRECATED);
+      $this->superUserAccessPolicy = \Drupal::getContainer()->getParameter('security.enable_super_user') ?? TRUE;
     }
-    $this->userNameValidator = $userNameValidator;
   }
 
   /**
@@ -99,9 +110,13 @@ class SiteConfigureForm extends ConfigFormBase {
     return new static(
       $container->getParameter('app.root'),
       $container->getParameter('site.path'),
-      $container->get('entity_type.manager')->getStorage('user'),
+      $container->get('entity_type.manager'),
       $container->get('module_installer'),
       $container->get('user.name_validator'),
+      // In order to disable the super user policy this must be set to FALSE. If
+      // the container parameter is missing then the policy is enabled. See
+      // \Drupal\Core\DependencyInjection\Compiler\SuperUserAccessPolicyPass.
+      $container->getParameter('security.enable_super_user') ?? TRUE,
     );
   }
 
@@ -177,9 +192,16 @@ class SiteConfigureForm extends ConfigFormBase {
       '#access' => empty($install_state['config_install_path']),
     ];
 
+    if (count($this->getAdminRoles()) === 0 && $this->superUserAccessPolicy === FALSE) {
+      $account_label = $this->t('Site account');
+    }
+    else {
+      $account_label = $this->t('Site maintenance account');
+    }
+
     $form['admin_account'] = [
       '#type' => 'fieldgroup',
-      '#title' => $this->t('Site maintenance account'),
+      '#title' => $account_label,
     ];
     $form['admin_account']['account']['name'] = [
       '#type' => 'textfield',
@@ -300,6 +322,7 @@ class SiteConfigureForm extends ConfigFormBase {
     }
 
     // We created user 1 with placeholder values. Let's save the real values.
+    /** @var \Drupal\user\UserInterface $account */
     $account = $this->userStorage->load(1);
     $account->init = $account->mail = $account_values['mail'];
     $account->roles = $account->getRoles();
@@ -307,7 +330,38 @@ class SiteConfigureForm extends ConfigFormBase {
     $account->timezone = $form_state->getValue('date_default_timezone');
     $account->pass = $account_values['pass'];
     $account->name = $account_values['name'];
+
+    // Ensure user 1 has an administrator role if one exists.
+    /** @var \Drupal\user\RoleInterface[] $admin_roles */
+    $admin_roles = $this->getAdminRoles();
+    if (count(array_intersect($account->getRoles(), array_keys($admin_roles))) === 0) {
+      if (count($admin_roles) > 0) {
+        foreach ($admin_roles as $role) {
+          $account->addRole($role->id());
+        }
+      }
+      elseif ($this->superUserAccessPolicy === FALSE) {
+        $this->messenger()->addWarning($this->t(
+          'The user %username does not have administrator access. For more information, see the documentation on <a href="@secure-user-1-docs">securing the admin super user</a>.',
+          [
+            '%username' => $account->getDisplayName(),
+            '@secure-user-1-docs' => 'https://www.drupal.org/docs/administering-a-drupal-site/security-in-drupal/securing-the-admin-super-user-1#s-disable-the-super-user-access-policy',
+          ]
+        ));
+      }
+    }
+
     $account->save();
   }
 
+  /**
+   * Returns the list of admin roles.
+   *
+   * @return \Drupal\user\RoleInterface[]
+   *   The list of admin roles.
+   */
+  protected function getAdminRoles(): array {
+    return $this->entityTypeManager->getStorage('user_role')->loadByProperties(['is_admin' => TRUE]);
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Installer/InstallerAccessPolicy.php b/core/lib/Drupal/Core/Installer/InstallerAccessPolicy.php
new file mode 100644
index 00000000000..819578f2a07
--- /dev/null
+++ b/core/lib/Drupal/Core/Installer/InstallerAccessPolicy.php
@@ -0,0 +1,44 @@
+<?php
+
+namespace Drupal\Core\Installer;
+
+use Drupal\Core\Session\AccessPolicyBase;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\Core\Session\CalculatedPermissionsItem;
+use Drupal\Core\Session\RefinableCalculatedPermissionsInterface;
+
+/**
+ * Grants user 1 an all access pass during install.
+ *
+ * @internal
+ *   The policy is only to be used by the installer.
+ */
+final class InstallerAccessPolicy extends AccessPolicyBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function calculatePermissions(AccountInterface $account, string $scope): RefinableCalculatedPermissionsInterface {
+    $calculated_permissions = parent::calculatePermissions($account, $scope);
+
+    // Prevent the access policy from working when not in the installer.
+    if (((int) $account->id()) !== 1 || !InstallerKernel::installationAttempted()) {
+      return $calculated_permissions;
+    }
+
+    return $calculated_permissions->addItem(new CalculatedPermissionsItem([], TRUE));
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPersistentCacheContexts(): array {
+    // Note that cache contexts in the installer are ignored because
+    // \Drupal\Core\Installer\NormalInstallerServiceProvider::register() changes
+    // everything to use a memory cache. If this was not the case, then this
+    // should also return a cache context related to the return value of
+    // \Drupal\Core\Installer\InstallerKernel::installationAttempted().
+    return ['user.is_super_user'];
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Installer/NormalInstallerServiceProvider.php b/core/lib/Drupal/Core/Installer/NormalInstallerServiceProvider.php
index a8c6ec84aa4..7c8d8129317 100644
--- a/core/lib/Drupal/Core/Installer/NormalInstallerServiceProvider.php
+++ b/core/lib/Drupal/Core/Installer/NormalInstallerServiceProvider.php
@@ -12,6 +12,7 @@ use Symfony\Component\DependencyInjection\Compiler\InlineServiceDefinitionsPass;
 use Symfony\Component\DependencyInjection\Compiler\RemoveUnusedDefinitionsPass;
 use Symfony\Component\DependencyInjection\Compiler\ReplaceAliasByActualDefinitionPass;
 use Symfony\Component\DependencyInjection\Compiler\ResolveHotPathPass;
+use Symfony\Component\DependencyInjection\Definition;
 use Symfony\Component\DependencyInjection\Reference;
 
 /**
@@ -33,6 +34,9 @@ class NormalInstallerServiceProvider implements ServiceProviderInterface {
    * {@inheritdoc}
    */
   public function register(ContainerBuilder $container) {
+    // During the installer user 1 is a superuser.
+    $container->setDefinition(InstallerAccessPolicy::class, (new Definition())->addTag('access_policy')->setPublic(FALSE));
+
     // Replace cache services with in-memory implementations. The results in
     // less queries to set caches which will only be cleared on the next module
     // install.
diff --git a/core/profiles/demo_umami/demo_umami.install b/core/profiles/demo_umami/demo_umami.install
index 5c0c94669a6..5404f934a2d 100644
--- a/core/profiles/demo_umami/demo_umami.install
+++ b/core/profiles/demo_umami/demo_umami.install
@@ -5,7 +5,6 @@
  * Install, update and uninstall functions for the demo_umami installation profile.
  */
 
-use Drupal\user\Entity\User;
 use Drupal\shortcut\Entity\Shortcut;
 
 /**
@@ -34,12 +33,6 @@ function demo_umami_requirements($phase) {
  * @see system_install()
  */
 function demo_umami_install() {
-  // Assign user 1 the "administrator" role.
-  /** @var \Drupal\user\Entity\User $user */
-  $user = User::load(1);
-  $user->addRole('administrator');
-  $user->save();
-
   // We install some menu links, so we have to rebuild the router, to ensure the
   // menu links are valid.
   \Drupal::service('router.builder')->rebuildIfNeeded();
diff --git a/core/profiles/standard/standard.install b/core/profiles/standard/standard.install
index 22bb1877bd5..6fda4647f17 100644
--- a/core/profiles/standard/standard.install
+++ b/core/profiles/standard/standard.install
@@ -5,7 +5,6 @@
  * Install, update and uninstall functions for the standard installation profile.
  */
 
-use Drupal\user\Entity\User;
 use Drupal\shortcut\Entity\Shortcut;
 
 /**
@@ -16,12 +15,6 @@ use Drupal\shortcut\Entity\Shortcut;
  * @see system_install()
  */
 function standard_install() {
-  // Assign user 1 the "administrator" role.
-  /** @var \Drupal\user\Entity\User $user */
-  $user = User::load(1);
-  $user->addRole('administrator');
-  $user->save();
-
   // Populate the default shortcut set.
   $shortcut = Shortcut::create([
     'shortcut_set' => 'default',
diff --git a/core/tests/Drupal/FunctionalTests/Installer/SuperUserAccessInstallTest.php b/core/tests/Drupal/FunctionalTests/Installer/SuperUserAccessInstallTest.php
new file mode 100644
index 00000000000..826b73504df
--- /dev/null
+++ b/core/tests/Drupal/FunctionalTests/Installer/SuperUserAccessInstallTest.php
@@ -0,0 +1,150 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\FunctionalTests\Installer;
+
+use Drupal\Core\Serialization\Yaml;
+use Drupal\user\Entity\User;
+
+/**
+ * Tests superuser access and the installer.
+ *
+ * @group Installer
+ */
+class SuperUserAccessInstallTest extends InstallerTestBase {
+
+  /**
+   * Message when the logged-in user does not have admin access after install.
+   *
+   * @see \Drupal\Core\Installer\Form\SiteConfigureForm::submitForm())
+   */
+  protected const NO_ACCESS_MESSAGE = 'The user %s does not have administrator access. For more information, see the documentation on securing the admin super user.';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $profile = 'superuser';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function prepareEnvironment() {
+    parent::prepareEnvironment();
+    $info = [
+      'type' => 'profile',
+      'core_version_requirement' => '*',
+      'name' => 'Superuser testing profile',
+    ];
+    // File API functions are not available yet.
+    $path = $this->siteDirectory . '/profiles/superuser';
+    mkdir($path, 0777, TRUE);
+    file_put_contents("$path/superuser.info.yml", Yaml::encode($info));
+
+    file_put_contents("$path/superuser.install", $this->getProvidedData()['install_code']);
+
+    $services = Yaml::decode(file_get_contents(DRUPAL_ROOT . '/sites/default/default.services.yml'));
+    $services['parameters']['security.enable_super_user'] = $this->getProvidedData()['super_user_policy'];
+    file_put_contents(DRUPAL_ROOT . '/' . $this->siteDirectory . '/services.yml', Yaml::encode($services));
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUpSite() {
+    if ($this->getProvidedData()['super_user_policy'] === FALSE && empty($this->getProvidedData()['expected_roles'])) {
+      $this->assertSession()->pageTextContains('Site account');
+      $this->assertSession()->pageTextNotContains('Site maintenance account');
+    }
+    else {
+      $this->assertSession()->pageTextNotContains('Site account');
+      $this->assertSession()->pageTextContains('Site maintenance account');
+    }
+    parent::setUpSite();
+  }
+
+  /**
+   * Confirms that the installation succeeded.
+   *
+   * @dataProvider getInstallTests
+   */
+  public function testInstalled(bool $expected_runtime_has_permission, bool $expected_no_access_message, array $expected_roles): void {
+    $user = User::load(1);
+    $this->assertSame($expected_runtime_has_permission, $user->hasPermission('administer software updates'));
+    $this->assertTrue(\Drupal::state()->get('admin_permission_in_installer'));
+    $message = sprintf(static::NO_ACCESS_MESSAGE, $this->rootUser->getDisplayName());
+    if ($expected_no_access_message) {
+      $this->assertSession()->pageTextContains($message);
+    }
+    else {
+      $this->assertSession()->pageTextNotContains($message);
+    }
+    $this->assertSame($expected_roles, $user->getRoles(TRUE));
+  }
+
+  public static function getInstallTests(): array {
+    $test_cases = [];
+    $test_cases['runtime super user policy enabled'] = [
+      'expected_runtime_has_permission' => TRUE,
+      'expected_no_access_message' => FALSE,
+      'expected_roles' => [],
+      'install_code' => <<<PHP
+      <?php
+      function superuser_install() {
+        \$user = \Drupal\user\Entity\User::load(1);
+        \Drupal::state()->set('admin_permission_in_installer', \$user->hasPermission('administer software updates'));
+      }
+      PHP,
+      'super_user_policy' => TRUE,
+    ];
+
+    $test_cases['no super user policy enabled and no admin role'] = [
+      'expected_runtime_has_permission' => FALSE,
+      'expected_no_access_message' => TRUE,
+      'expected_roles' => [],
+      'install_code' => $test_cases['runtime super user policy enabled']['install_code'],
+      'super_user_policy' => FALSE,
+    ];
+
+    $test_cases['no super user policy enabled and admin role'] = [
+      'expected_runtime_has_permission' => TRUE,
+      'expected_no_access_message' => FALSE,
+      'expected_roles' => ['admin_role'],
+      'install_code' => <<<PHP
+      <?php
+      function superuser_install() {
+        \$user = \Drupal\user\Entity\User::load(1);
+        \Drupal::state()->set('admin_permission_in_installer', \$user->hasPermission('administer software updates'));
+        \Drupal\user\Entity\Role::create(['id' => 'admin_role', 'label' => 'Admin role'])->setIsAdmin(TRUE)->save();
+        \Drupal\user\Entity\Role::create(['id' => 'another_role', 'label' => 'Another role'])->save();
+      }
+      PHP,
+      'super_user_policy' => FALSE,
+    ];
+
+    $test_cases['no super user policy enabled and multiple admin role'] = [
+      'expected_runtime_has_permission' => TRUE,
+      'expected_no_access_message' => FALSE,
+      'expected_roles' => ['admin_role', 'another_admin_role'],
+      'install_code' => <<<PHP
+      <?php
+      function superuser_install() {
+        \$user = \Drupal\user\Entity\User::load(1);
+        \Drupal::state()->set('admin_permission_in_installer', \$user->hasPermission('administer software updates'));
+        \Drupal\user\Entity\Role::create(['id' => 'admin_role', 'label' => 'Admin role'])->setIsAdmin(TRUE)->save();
+        \Drupal\user\Entity\Role::create(['id' => 'another_admin_role', 'label' => 'Another admin role'])->setIsAdmin(TRUE)->save();
+        \Drupal\user\Entity\Role::create(['id' => 'another_role', 'label' => 'Another role'])->save();
+      }
+      PHP,
+      'super_user_policy' => FALSE,
+    ];
+
+    return $test_cases;
+  }
+
+}