diff --git a/app/models/application_setting.rb b/app/models/application_setting.rb
index af7730351750f19e802aee495e4ebef7bbb1b052..85ef4aeb6060cdf30e21b6ab6c3dab9727f40136 100644
--- a/app/models/application_setting.rb
+++ b/app/models/application_setting.rb
@@ -71,6 +71,9 @@ def self.kroki_formats_attributes
       },
       excalidraw: {
         label: 'Excalidraw'
+      },
+      mermaid: {
+        label: 'Mermaid'
       }
     }
   end
@@ -1264,6 +1267,8 @@ def kroki_format_supported?(diagram_type)
       return kroki_formats_excalidraw
     when 'bpmn'
       return kroki_formats_bpmn
+    when 'mermaid'
+      return kroki_formats_mermaid
     end
 
     return kroki_formats_blockdiag if ::Gitlab::Kroki::BLOCKDIAG_FORMATS.include?(diagram_type)
diff --git a/app/models/application_setting_implementation.rb b/app/models/application_setting_implementation.rb
index c1c2cce0043bd88c7271aa083e62205debb3da08..f574c4033d9abcae4009b57d9de08f230e7d1eeb 100644
--- a/app/models/application_setting_implementation.rb
+++ b/app/models/application_setting_implementation.rb
@@ -284,7 +284,7 @@ def defaults # rubocop:disable Metrics/AbcSize
         container_registry_expiration_policies_caching: true,
         kroki_enabled: false,
         kroki_url: nil,
-        kroki_formats: { blockdiag: false, bpmn: false, excalidraw: false },
+        kroki_formats: { blockdiag: false, bpmn: false, excalidraw: false, mermaid: false },
         rate_limiting_response_text: nil,
         whats_new_variant: 0,
         user_deactivation_emails_enabled: true,
diff --git a/app/validators/json_schemas/application_setting_kroki_formats.json b/app/validators/json_schemas/application_setting_kroki_formats.json
index 4dfa710abeadc6ea6461e4f70d600007acf03a4a..056d48ecdd9f2b555e9f8e178a61621bc304e32d 100644
--- a/app/validators/json_schemas/application_setting_kroki_formats.json
+++ b/app/validators/json_schemas/application_setting_kroki_formats.json
@@ -3,9 +3,18 @@
   "description": "Kroki formats",
   "type": "object",
   "properties": {
-    "bpmn": { "type": "boolean" },
-    "excalidraw": { "type": "boolean" },
-    "blockdiag": { "type": "boolean" }
+    "bpmn": {
+      "type": "boolean"
+    },
+    "excalidraw": {
+      "type": "boolean"
+    },
+    "blockdiag": {
+      "type": "boolean"
+    },
+    "mermaid": {
+      "type": "boolean"
+    }
   },
   "additionalProperties": false
 }
diff --git a/config/application_setting_columns/kroki_formats.yml b/config/application_setting_columns/kroki_formats.yml
index 942de3b5f2866c127c5bd3f5d880c540f29dc527..22efcb38be771b3d73b5c27249ad6afac13a3cd7 100644
--- a/config/application_setting_columns/kroki_formats.yml
+++ b/config/application_setting_columns/kroki_formats.yml
@@ -6,8 +6,8 @@ column: kroki_formats
 db_type: jsonb
 default: "'{}'::jsonb"
 description: 'Additional formats supported by the Kroki instance. Possible values
-  are `true` or `false` for formats `bpmn`, `blockdiag`, and `excalidraw` in the format
-  `<format>: true` or `<format>: false`.'
+  are `true` or `false` for formats `bpmn`, `blockdiag`, `excalidraw`, and `mermaid`
+  in the format `<format>: true` or `<format>: false`.'
 encrypted: false
 gitlab_com_different_than_default: false
 jihu: false
diff --git a/doc/api/settings.md b/doc/api/settings.md
index 94202803019be2dba6f964613c2369046c81fc13..7f25b302f01167d80308501d4a287a9be4d15f40 100644
--- a/doc/api/settings.md
+++ b/doc/api/settings.md
@@ -691,7 +691,7 @@ to configure other related settings. These requirements are
 | `inactive_resource_access_tokens_delete_after_days`| integer | no                                   | Specifies retention period for inactive project and group access tokens. Default is `30`. |
 | `kroki_enabled`                          | boolean          | no                                   | (**If enabled, requires**: `kroki_url`) Enable [Kroki integration](../administration/integration/kroki.md). Default is `false`. |
 | `kroki_url`                              | string           | required by: `kroki_enabled`         | The Kroki instance URL for integration. |
-| `kroki_formats`                          | object           | no                                   | Additional formats supported by the Kroki instance. Possible values are `true` or `false` for formats `bpmn`, `blockdiag`, and `excalidraw` in the format `<format>: true` or `<format>: false`. |
+| `kroki_formats`                          | object           | no                                   | Additional formats supported by the Kroki instance. Possible values are `true` or `false` for formats `bpmn`, `blockdiag`, `excalidraw`, and `mermaid` in the format `<format>: true` or `<format>: false`. |
 | `plantuml_enabled`                       | boolean          | no                                   | (**If enabled, requires**: `plantuml_url`) Enable [PlantUML integration](../administration/integration/plantuml.md). Default is `false`. |
 | `plantuml_url`                           | string           | required by: `plantuml_enabled`      | The PlantUML instance URL for integration. |
 | `polling_interval_multiplier`            | float            | no                                   | Interval multiplier used by endpoints that perform polling. Set to `0` to disable polling. |
diff --git a/lib/gitlab/kroki.rb b/lib/gitlab/kroki.rb
index 84dc081d9d7cae33e6ff92a4f950c4d9ccda329c..ed5418e6ab58cf57bb721616676b6ef1fb664e21 100644
--- a/lib/gitlab/kroki.rb
+++ b/lib/gitlab/kroki.rb
@@ -14,7 +14,12 @@ module Kroki
       packetdiag
       rackdiag
     ].freeze
-    DIAGRAMS_FORMATS = (::AsciidoctorExtensions::Kroki::SUPPORTED_DIAGRAM_NAMES - %w[mermaid]).freeze
+
+    # We used to explicitly remove 'mermaid' from this list, but now we allow Kroki
+    # to preferentially render them, *if* the administrator has explicitly enabled it
+    # --- Mermaid requires a companion server for Kroki.
+    # See https://gitlab.com/gitlab-org/gitlab/-/work_items/498764.
+    DIAGRAMS_FORMATS = ::AsciidoctorExtensions::Kroki::SUPPORTED_DIAGRAM_NAMES.dup.freeze
     DIAGRAMS_FORMATS_WO_PLANTUML = (DIAGRAMS_FORMATS - %w[plantuml]).freeze
 
     # Get the list of diagram formats that are currently enabled
diff --git a/spec/helpers/application_settings_helper_spec.rb b/spec/helpers/application_settings_helper_spec.rb
index 9cc0d23449dfdb1f11e7bd700bc2108666a8861a..1bb0f041519d4ba1f4061b98e8c60f571809aca4 100644
--- a/spec/helpers/application_settings_helper_spec.rb
+++ b/spec/helpers/application_settings_helper_spec.rb
@@ -249,7 +249,8 @@
 
     before do
       helper.instance_variable_set(:@application_setting, application_setting)
-      stub_application_setting(kroki_formats: { 'blockdiag' => true, 'bpmn' => false, 'excalidraw' => false })
+      stub_application_setting(kroki_formats: { 'blockdiag' => true, 'bpmn' => false, 'excalidraw' => false,
+                                                'mermaid' => true })
     end
 
     it 'returns available formats correctly' do
@@ -269,6 +270,11 @@
             name: 'kroki_formats_excalidraw',
             label: 'Excalidraw',
             value: false
+          },
+          {
+            name: 'kroki_formats_mermaid',
+            label: 'Mermaid',
+            value: true
           }
         ])
     end
diff --git a/spec/lib/gitlab/kroki_spec.rb b/spec/lib/gitlab/kroki_spec.rb
index ab888c3b0155bbd884c77cd63c409966bfc62e14..333784db0238617458fb3368ab9a148558c8906f 100644
--- a/spec/lib/gitlab/kroki_spec.rb
+++ b/spec/lib/gitlab/kroki_spec.rb
@@ -17,6 +17,7 @@ def default_formats
       'blockdiag'  | (default_formats + %w[actdiag blockdiag nwdiag packetdiag rackdiag seqdiag])
       'bpmn'       | (default_formats + %w[bpmn])
       'excalidraw' | (default_formats + %w[excalidraw])
+      'mermaid'    | (default_formats + %w[mermaid])
     end
 
     with_them do
diff --git a/spec/models/application_setting_spec.rb b/spec/models/application_setting_spec.rb
index 33dd00c5deeba9995b8f2891fb853e336be3eb83..dd3a3874c5f235dc6af941ee7d070e7662b1e85e 100644
--- a/spec/models/application_setting_spec.rb
+++ b/spec/models/application_setting_spec.rb
@@ -159,7 +159,7 @@
         invisible_captcha_enabled: false,
         issues_create_limit: 300,
         jira_connect_public_key_storage_enabled: false,
-        kroki_formats: { 'blockdiag' => false, 'bpmn' => false, 'excalidraw' => false },
+        kroki_formats: { 'blockdiag' => false, 'bpmn' => false, 'excalidraw' => false, 'mermaid' => false },
         local_markdown_version: 0,
         lock_maven_package_requests_forwarding: false,
         lock_npm_package_requests_forwarding: false,
@@ -2388,6 +2388,7 @@ def expect_invalid
 
     it 'returns false when the diagram type is optional and not enabled' do
       expect(setting.kroki_format_supported?('bpmn')).to be(false)
+      expect(setting.kroki_format_supported?('mermaid')).to be(false)
     end
 
     it 'returns true when the diagram type is enabled by default' do
@@ -2403,10 +2404,11 @@ def expect_invalid
 
   describe 'kroki_formats' do
     it 'returns the value for kroki_formats' do
-      setting.kroki_formats = { blockdiag: true, bpmn: false, excalidraw: true }
+      setting.kroki_formats = { blockdiag: true, bpmn: false, excalidraw: true, mermaid: true }
       expect(setting.kroki_formats_blockdiag).to be(true)
       expect(setting.kroki_formats_bpmn).to be(false)
       expect(setting.kroki_formats_excalidraw).to be(true)
+      expect(setting.kroki_formats_mermaid).to be(true)
     end
   end