diff --git a/app/lib/activitypub/activity/create.rb b/app/lib/activitypub/activity/create.rb
index e55532f3ab..c133ef673a 100644
--- a/app/lib/activitypub/activity/create.rb
+++ b/app/lib/activitypub/activity/create.rb
@@ -46,8 +46,12 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
     )
   end
 
+  def reject_pattern?
+    Setting.reject_pattern.present? && @object['content']&.match?(Setting.reject_pattern)
+  end
+
   def create_status
-    return reject_payload! if unsupported_object_type? || non_matching_uri_hosts?(@account.uri, object_uri) || tombstone_exists? || !related_to_local_activity?
+    return reject_payload! if unsupported_object_type? || non_matching_uri_hosts?(@account.uri, object_uri) || tombstone_exists? || !related_to_local_activity? || reject_pattern?
 
     with_redis_lock("create:#{object_uri}") do
       return if delete_arrived_first?(object_uri) || poll_vote?
diff --git a/app/models/form/admin_settings.rb b/app/models/form/admin_settings.rb
index 095733673e..d284b929fe 100644
--- a/app/models/form/admin_settings.rb
+++ b/app/models/form/admin_settings.rb
@@ -45,6 +45,7 @@ class Form::AdminSettings
     status_page_url
     captcha_enabled
     authorized_fetch
+    reject_pattern
   ).freeze
 
   INTEGER_KEYS = %i(
@@ -95,6 +96,7 @@ class Form::AdminSettings
   validates :show_domain_blocks_rationale, inclusion: { in: %w(disabled users all) }, if: -> { defined?(@show_domain_blocks_rationale) }
   validates :media_cache_retention_period, :content_cache_retention_period, :backups_retention_period, numericality: { only_integer: true }, allow_blank: true, if: -> { defined?(@media_cache_retention_period) || defined?(@content_cache_retention_period) || defined?(@backups_retention_period) }
   validates :site_short_description, length: { maximum: 200 }, if: -> { defined?(@site_short_description) }
+  validates :reject_pattern, regexp_syntax: true, if: -> { defined?(@reject_pattern) }
   validates :status_page_url, url: true, allow_blank: true
   validate :validate_site_uploads
 
diff --git a/app/validators/regexp_syntax_validator.rb b/app/validators/regexp_syntax_validator.rb
new file mode 100644
index 0000000000..57ecf882c2
--- /dev/null
+++ b/app/validators/regexp_syntax_validator.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+class RegexpSyntaxValidator < ActiveModel::EachValidator
+  def validate_each(record, attribute, value)
+    return if value.blank?
+
+    begin
+      Regexp.compile(value)
+    rescue RegexpError => e
+      record.errors.add(attribute, I18n.t('applications.invalid_regexp', message: e.message))
+    end
+  end
+end
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 9d739be07f..4389793663 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -766,6 +766,10 @@ en:
         all: To everyone
         disabled: To no one
         users: To logged-in local users
+      others:
+        activitypub: ActivityPub
+        preamble: Other settings, including customizing behavior
+        title: Other settings
       registrations:
         preamble: Control who can create an account on your server.
         title: Registrations
@@ -774,6 +778,9 @@ en:
           approved: Approval required for sign up
           none: Nobody can sign up
           open: Anyone can sign up
+      reject_pattern:
+        desc_html: Set a regular expression pattern to inspect Create Activity content, and refuse Activity if you match
+        title: Reject Pattern
       security:
         authorized_fetch: Require authentication from federated servers
         authorized_fetch_hint: Requiring authentication from federated servers enables stricter enforcement of both user-level and server-level blocks. However, this comes at the cost of a performance penalty, reduces the reach of your replies, and may introduce compatibility issues with some federated services. In addition, this will not prevent dedicated actors from fetching your public posts and accounts.
@@ -1029,6 +1036,7 @@ en:
   applications:
     created: Application successfully created
     destroyed: Application successfully deleted
+    invalid_regexp: "The provided Regexp is invalid: %{message}"
     logout: Logout
     regenerate_token: Regenerate access token
     token_regenerated: Access token successfully regenerated
diff --git a/config/settings.yml b/config/settings.yml
index 24af0a786e..355fc5f515 100644
--- a/config/settings.yml
+++ b/config/settings.yml
@@ -46,6 +46,7 @@ defaults: &defaults
   require_invite_text: false
   backups_retention_period: 7
   captcha_enabled: false
+  reject_pattern: ''
 
 development:
   <<: *defaults