diff --git a/config/locales/server.en.yml b/config/locales/server.en.yml
index e9fb197e787..bbb3b520531 100644
--- a/config/locales/server.en.yml
+++ b/config/locales/server.en.yml
@@ -1281,6 +1281,8 @@ en:
     approve_post_count: "The amount of posts from a new or basic user that must be approved"
     approve_unless_trust_level: "Posts for users below this trust level must be approved"
     notify_about_queued_posts_after: "If there are posts that have been waiting to be reviewed for more than this many hours, an email will be sent to the contact_email. Set to 0 to disable these emails."
+    auto_close_messages_post_count: "Maximum number of posts allowed in a message before it is automatically closed (0 to disable)"
+    auto_close_topics_post_count: "Maximum number of posts allowed in a topic before it is automatically closed (0 to disable)"
 
     default_email_digest_frequency: "How often users receive digest emails by default."
     default_include_tl0_in_digests: "Include posts from new users in digest emails by default. Users can change this in their preferences."
@@ -1391,6 +1393,12 @@ en:
     archived_disabled: "This topic is now unarchived. It is no longer frozen, and can be changed."
     closed_enabled: "This topic is now closed. New replies are no longer allowed."
     closed_disabled: "This topic is now opened. New replies are allowed."
+    autoclosed_message_max_posts:
+      one: "This message was automatically closed after reaching the limit of 1 post per message"
+      other: "This message was automatically closed after reaching the limit of %{count} posts per message"
+    autoclosed_topic_max_posts:
+      one: "This topic was automatically closed after reaching the limit of 1 post per topic"
+      other: "This topic was automatically closed after reaching the limit of %{count} posts per topic"
     autoclosed_enabled_days:
       one: "This topic was automatically closed after 1 day. New replies are no longer allowed."
       other: "This topic was automatically closed after %{count} days. New replies are no longer allowed."
diff --git a/config/site_settings.yml b/config/site_settings.yml
index d20c56245ec..d88950534ae 100644
--- a/config/site_settings.yml
+++ b/config/site_settings.yml
@@ -505,6 +505,8 @@ posting:
   notify_about_queued_posts_after:
     default: 24
     min: 0
+  auto_close_messages_post_count: 200
+  auto_close_topics_post_count: 10000
 
 email:
   email_time_window_mins:
diff --git a/lib/post_creator.rb b/lib/post_creator.rb
index 62bc2a57934..6b1790b208a 100644
--- a/lib/post_creator.rb
+++ b/lib/post_creator.rb
@@ -148,6 +148,8 @@ class PostCreator
       BadgeGranter.queue_badge_grant(Badge::Trigger::PostRevision, post: @post)
 
       trigger_after_events(@post)
+
+      auto_close
     end
 
     if @post || @spam
@@ -221,6 +223,26 @@ class PostCreator
     DiscourseEvent.trigger(:post_created, post, @opts, @user)
   end
 
+  def auto_close
+    if @post.topic.private_message? &&
+        !@post.topic.closed &&
+        SiteSetting.auto_close_messages_post_count > 0 &&
+        SiteSetting.auto_close_messages_post_count <= @post.topic.posts_count
+
+      @post.topic.update_status(:closed, true, Discourse.system_user,
+          message: I18n.t('topic_statuses.autoclosed_message_max_posts', count: SiteSetting.auto_close_messages_post_count))
+
+    elsif !@post.topic.private_message? &&
+        !@post.topic.closed &&
+        SiteSetting.auto_close_topics_post_count > 0 &&
+        SiteSetting.auto_close_topics_post_count <= @post.topic.posts_count
+
+      @post.topic.update_status(:closed, true, Discourse.system_user,
+          message: I18n.t('topic_statuses.autoclosed_topic_max_posts', count: SiteSetting.auto_close_messages_post_count))
+
+    end
+  end
+
   def transaction(&blk)
     Post.transaction do
       if new_topic?
diff --git a/spec/components/post_creator_spec.rb b/spec/components/post_creator_spec.rb
index 8675fdf77e6..762649bc83a 100644
--- a/spec/components/post_creator_spec.rb
+++ b/spec/components/post_creator_spec.rb
@@ -547,6 +547,32 @@ describe PostCreator do
     end
   end
 
+  context 'auto closing' do
+    it 'closes private messages that have more than N posts' do
+      SiteSetting.auto_close_messages_post_count = 2
+
+      admin = Fabricate(:admin)
+
+      post1 = create_post(archetype: Archetype.private_message,
+                          target_usernames: [admin.username])
+
+      _post2 = create_post(user: post1.user, topic_id: post1.topic_id)
+
+      post1.topic.reload
+      expect(post1.topic.closed).to eq(true)
+    end
+
+    it 'closes topics that have more than N posts' do
+      SiteSetting.auto_close_topics_post_count = 2
+
+      post1 = create_post
+      _post2 = create_post(user: post1.user, topic_id: post1.topic_id)
+
+      post1.topic.reload
+      expect(post1.topic.closed).to eq(true)
+    end
+  end
+
   context 'private message to group' do
     let(:target_user1) { Fabricate(:coding_horror) }
     let(:target_user2) { Fabricate(:moderator) }