diff --git a/app/assets/javascripts/admin/addon/components/watched-word-form.js b/app/assets/javascripts/admin/addon/components/watched-word-form.js
index cf0ceb3f455..cf957148e2b 100644
--- a/app/assets/javascripts/admin/addon/components/watched-word-form.js
+++ b/app/assets/javascripts/admin/addon/components/watched-word-form.js
@@ -6,6 +6,7 @@ import Component from "@ember/component";
 import I18n from "I18n";
 import WatchedWord from "admin/models/watched-word";
 import bootbox from "bootbox";
+import { equal } from "@ember/object/computed";
 import { isEmpty } from "@ember/utils";
 import { schedule } from "@ember/runloop";
 
@@ -15,10 +16,8 @@ export default Component.extend({
   actionKey: null,
   showMessage: false,
 
-  @discourseComputed("actionKey")
-  canReplace(actionKey) {
-    return actionKey === "replace";
-  },
+  canReplace: equal("actionKey", "replace"),
+  canTag: equal("actionKey", "tag"),
 
   @discourseComputed("regularExpressions")
   placeholderKey(regularExpressions) {
@@ -61,7 +60,7 @@ export default Component.extend({
 
         const watchedWord = WatchedWord.create({
           word: this.word,
-          replacement: this.canReplace ? this.replacement : null,
+          replacement: this.canReplace || this.canTag ? this.replacement : null,
           action: this.actionKey,
         });
 
diff --git a/app/assets/javascripts/admin/addon/templates/components/watched-word-form.hbs b/app/assets/javascripts/admin/addon/templates/components/watched-word-form.hbs
index 79231fa8044..66b148c303f 100644
--- a/app/assets/javascripts/admin/addon/templates/components/watched-word-form.hbs
+++ b/app/assets/javascripts/admin/addon/templates/components/watched-word-form.hbs
@@ -10,6 +10,13 @@
   </div>
 {{/if}}
 
+{{#if canTag}}
+  <div class="watched-word-input">
+    <label for="watched-tag">{{i18n "admin.watched_words.form.tag_label"}}</label>
+    {{text-field id="watched-tag" value=replacement disabled=formSubmitted class="watched-word-input" autocorrect="off" autocapitalize="off" placeholderKey="admin.watched_words.form.tag_placeholder"}}
+  </div>
+{{/if}}
+
 {{d-button class="btn-default" action=(action "submit") disabled=formSubmitted label="admin.watched_words.form.add"}}
 
 {{#if showMessage}}
diff --git a/app/jobs/regular/process_post.rb b/app/jobs/regular/process_post.rb
index 6ba04d4f5b2..9ff98cae223 100644
--- a/app/jobs/regular/process_post.rb
+++ b/app/jobs/regular/process_post.rb
@@ -29,13 +29,13 @@ module Jobs
         cooked = cp.html
 
         if cooked != (recooked || orig_cooked)
-
           if orig_cooked.present? && cooked.blank?
             # TODO stop/restart the worker if needed, let's gather a few here first
             Rails.logger.warn("Cooked post processor in FATAL state, bypassing. You need to urgently restart sidekiq\norig: #{orig_cooked}\nrecooked: #{recooked}\ncooked: #{cooked}\npost id: #{post.id}")
           else
             post.update_column(:cooked, cp.html)
             extract_links(post)
+            auto_tag(post) if SiteSetting.tagging_enabled? && post.post_number == 1
             post.publish_change_to_clients! :revised
           end
         end
@@ -60,6 +60,25 @@ module Jobs
       TopicLink.extract_from(post)
       QuotedPost.extract_from(post)
     end
+
+    def auto_tag(post)
+      word_watcher = WordWatcher.new(post.raw)
+
+      old_tags = post.topic.tags.pluck(:name).to_set
+      new_tags = old_tags.dup
+
+      WordWatcher.words_for_action(:tag).each do |word, tags|
+        new_tags += tags.split(",") if word_watcher.matches?(word)
+      end
+
+      if old_tags != new_tags
+        post.revise(
+          Discourse.system_user,
+          tags: new_tags.to_a,
+          edit_reason: I18n.t(:watched_words_auto_tag)
+        )
+      end
+    end
   end
 
 end
diff --git a/app/models/watched_word.rb b/app/models/watched_word.rb
index 200059978e3..2cbe61dcc12 100644
--- a/app/models/watched_word.rb
+++ b/app/models/watched_word.rb
@@ -8,7 +8,8 @@ class WatchedWord < ActiveRecord::Base
       censor: 2,
       require_approval: 3,
       flag: 4,
-      replace: 5
+      replace: 5,
+      tag: 6,
     )
   end
 
diff --git a/app/serializers/watched_word_serializer.rb b/app/serializers/watched_word_serializer.rb
index 65423716886..f96fbde53fd 100644
--- a/app/serializers/watched_word_serializer.rb
+++ b/app/serializers/watched_word_serializer.rb
@@ -8,6 +8,6 @@ class WatchedWordSerializer < ApplicationSerializer
   end
 
   def include_replacement?
-    action == :replace
+    action == :replace || action == :tag
   end
 end
diff --git a/app/services/word_watcher.rb b/app/services/word_watcher.rb
index 92d278b6b37..3665c72102e 100644
--- a/app/services/word_watcher.rb
+++ b/app/services/word_watcher.rb
@@ -8,7 +8,7 @@ class WordWatcher
 
   def self.words_for_action(action)
     words = WatchedWord.where(action: WatchedWord.actions[action.to_sym]).limit(1000)
-    if action.to_sym == :replace
+    if action.to_sym == :replace || action.to_sym == :tag
       words.pluck(:word, :replacement).to_h
     else
       words.pluck(:word)
@@ -31,7 +31,7 @@ class WordWatcher
   def self.word_matcher_regexp(action, raise_errors: false)
     words = get_cached_words(action)
     if words
-      if action.to_sym == :replace
+      if action.to_sym == :replace || action.to_sym == :tag
         words = words.keys
       end
       words = words.map do |w|
@@ -110,4 +110,12 @@ class WordWatcher
       false
     end
   end
+
+  def matches?(word)
+    if SiteSetting.watched_words_regular_expressions?
+      Regexp.new(word).match?(@raw)
+    else
+      @raw.include?(word)
+    end
+  end
 end
diff --git a/config/locales/client.en.yml b/config/locales/client.en.yml
index 5410a36cc6b..de65de44aa0 100644
--- a/config/locales/client.en.yml
+++ b/config/locales/client.en.yml
@@ -4621,18 +4621,22 @@ en:
           require_approval: "Require Approval"
           flag: "Flag"
           replace: "Replace"
+          tag: "Auto-tag"
         action_descriptions:
           block: "Prevent posts containing these words from being posted. The user will see an error message when they try to submit their post."
           censor: "Allow posts containing these words, but replace them with characters that hide the censored words."
           require_approval: "Posts containing these words will require approval by staff before they can be seen."
           flag: "Allow posts containing these words, but flag them as inappropriate so moderators can review them."
           replace: "Replace words in posts with other words or links"
+          tag: "Automatically tag posts with these words"
         form:
           label: "New Word"
           placeholder: "full word or * as wildcard"
           placeholder_regexp: "regular expression"
           replacement_label: "Replacement"
           replacement_placeholder: "example or https://example.com"
+          tag_label: "Tag"
+          tag_placeholder: "tag1,tag2,tag3"
           add: "Add"
           success: "Success"
           exists: "Already exists"
diff --git a/config/locales/server.en.yml b/config/locales/server.en.yml
index 562928b8b0a..43a183883d1 100644
--- a/config/locales/server.en.yml
+++ b/config/locales/server.en.yml
@@ -361,6 +361,7 @@ en:
   max_pm_recipients: "Sorry, you can send a message to maximum %{recipients_limit} recipients."
   pm_reached_recipients_limit: "Sorry, you can't have more than %{recipients_limit} recipients in a message."
   removed_direct_reply_full_quotes: "Automatically removed quote of whole previous post."
+  watched_words_auto_tag: "Automatically tagged topic"
   secure_upload_not_allowed_in_public_topic: "Sorry, the following secure upload(s) cannot be used in a public topic: %{upload_filenames}."
   create_pm_on_existing_topic: "Sorry, you can't create a PM on an existing topic."
   slow_mode_enabled: "This topic is in slow mode."
diff --git a/spec/jobs/process_post_spec.rb b/spec/jobs/process_post_spec.rb
index 35794be2959..c6f8ecb395d 100644
--- a/spec/jobs/process_post_spec.rb
+++ b/spec/jobs/process_post_spec.rb
@@ -77,6 +77,43 @@ describe Jobs::ProcessPost do
       post.reload
       expect(post.cooked).to eq(cooked)
     end
+
+    it "automatically tags first posts" do
+      SiteSetting.tagging_enabled = true
+
+      Fabricate(:watched_word, action: WatchedWord.actions[:tag], word: "Greetings?", replacement: "hello , world")
+
+      post = Fabricate(:post, raw: "Greeting", cooked: "")
+      Jobs::ProcessPost.new.execute(post_id: post.id)
+      expect(post.topic.reload.tags.pluck(:name)).to contain_exactly()
+
+      post = Fabricate(:post, raw: "Greetings", cooked: "")
+      Jobs::ProcessPost.new.execute(post_id: post.id)
+      expect(post.topic.reload.tags.pluck(:name)).to contain_exactly()
+
+      post = Fabricate(:post, raw: "Greetings?", cooked: "")
+      Jobs::ProcessPost.new.execute(post_id: post.id)
+      expect(post.topic.reload.tags.pluck(:name)).to contain_exactly("hello", "world")
+    end
+
+    it "automatically tags first posts (regex)" do
+      SiteSetting.tagging_enabled = true
+      SiteSetting.watched_words_regular_expressions = true
+
+      Fabricate(:watched_word, action: WatchedWord.actions[:tag], word: "Greetings?", replacement: "hello , world")
+
+      post = Fabricate(:post, raw: "Greeting", cooked: "")
+      Jobs::ProcessPost.new.execute(post_id: post.id)
+      expect(post.topic.reload.tags.pluck(:name)).to contain_exactly("hello", "world")
+
+      post = Fabricate(:post, raw: "Greetings", cooked: "")
+      Jobs::ProcessPost.new.execute(post_id: post.id)
+      expect(post.topic.reload.tags.pluck(:name)).to contain_exactly("hello", "world")
+
+      post = Fabricate(:post, raw: "Greetings?", cooked: "")
+      Jobs::ProcessPost.new.execute(post_id: post.id)
+      expect(post.topic.reload.tags.pluck(:name)).to contain_exactly("hello", "world")
+    end
   end
 
 end