diff --git a/app/models/site_setting.rb b/app/models/site_setting.rb
index fbe1b782d55..70b62602eec 100644
--- a/app/models/site_setting.rb
+++ b/app/models/site_setting.rb
@@ -94,6 +94,7 @@ class SiteSetting < ActiveRecord::Base
       SiteSetting.default_categories_watching.split("|"),
       SiteSetting.default_categories_tracking.split("|"),
       SiteSetting.default_categories_muted.split("|"),
+      SiteSetting.default_categories_watching_first_post.split("|")
     ].flatten.to_set
   end
 
diff --git a/app/models/user.rb b/app/models/user.rb
index 3de3020d17e..2d623817cc6 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -988,7 +988,7 @@ class User < ActiveRecord::Base
 
     values = []
 
-    %w{watching tracking muted}.each do |s|
+    %w{watching watching_first_post tracking muted}.each do |s|
       category_ids = SiteSetting.send("default_categories_#{s}").split("|")
       category_ids.each do |category_id|
         values << "(#{self.id}, #{category_id}, #{CategoryUser.notification_levels[s.to_sym]})"
diff --git a/config/locales/server.en.yml b/config/locales/server.en.yml
index 04b2e4d94e6..fb314c4dd00 100644
--- a/config/locales/server.en.yml
+++ b/config/locales/server.en.yml
@@ -1393,6 +1393,7 @@ en:
     default_categories_watching: "List of categories that are watched by default."
     default_categories_tracking: "List of categories that are tracked by default."
     default_categories_muted: "List of categories that are muted by default."
+    default_categories_watching_first_post: "List of first post in each new topic in these categories that are watched by default."
 
     max_user_api_reqs_per_day: "Maximum number of user API requests per key per day"
     max_user_api_reqs_per_minute: "Maximum number of user API requests per key per minute"
diff --git a/config/site_settings.yml b/config/site_settings.yml
index 92776b8eeae..57661444a80 100644
--- a/config/site_settings.yml
+++ b/config/site_settings.yml
@@ -1293,6 +1293,9 @@ user_preferences:
   default_categories_muted:
     type: category_list
     default: ''
+  default_categories_watching_first_post:
+    type: category_list
+    default: ''
 
 user_api:
   max_user_api_reqs_per_day:
diff --git a/lib/site_setting_validations.rb b/lib/site_setting_validations.rb
index e69bfc2f95d..0380c457a0a 100644
--- a/lib/site_setting_validations.rb
+++ b/lib/site_setting_validations.rb
@@ -21,6 +21,7 @@ module SiteSettingValidations
 
   def validate_default_categories_watching(new_val)
     default_categories_selected = [
+      SiteSetting.default_categories_watching_first_post.split("|"),
       SiteSetting.default_categories_tracking.split("|"),
       SiteSetting.default_categories_muted.split("|"),
     ].flatten.to_set
@@ -31,6 +32,7 @@ module SiteSettingValidations
   def validate_default_categories_tracking(new_val)
     default_categories_selected = [
       SiteSetting.default_categories_watching.split("|"),
+      SiteSetting.default_categories_watching_first_post.split("|"),
       SiteSetting.default_categories_muted.split("|"),
     ].flatten.to_set
 
@@ -40,12 +42,23 @@ module SiteSettingValidations
   def validate_default_categories_muted(new_val)
     default_categories_selected = [
       SiteSetting.default_categories_watching.split("|"),
+      SiteSetting.default_categories_watching_first_post.split("|"),
       SiteSetting.default_categories_tracking.split("|"),
     ].flatten.to_set
 
     validate_default_categories(new_val, default_categories_selected)
   end
 
+  def validate_default_categories_watching_first_post(new_val)
+    default_categories_selected = [
+      SiteSetting.default_categories_watching.split("|"),
+      SiteSetting.default_categories_tracking.split("|"),
+      SiteSetting.default_categories_muted.split("|"),
+    ].flatten.to_set
+
+    validate_default_categories(new_val, default_categories_selected)
+  end
+
   def validate_enable_s3_uploads(new_val)
     validate_error :s3_upload_bucket_is_required if new_val == "t" && SiteSetting.s3_upload_bucket.blank?
   end
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index cddc4b50a89..3a32c5e4854 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -1257,6 +1257,7 @@ describe User do
       SiteSetting.default_categories_watching = "1"
       SiteSetting.default_categories_tracking = "2"
       SiteSetting.default_categories_muted = "3"
+      SiteSetting.default_categories_watching_first_post = "4"
     end
 
     it "has overriden preferences" do
@@ -1279,6 +1280,7 @@ describe User do
       expect(CategoryUser.lookup(user, :watching).pluck(:category_id)).to eq([1])
       expect(CategoryUser.lookup(user, :tracking).pluck(:category_id)).to eq([2])
       expect(CategoryUser.lookup(user, :muted).pluck(:category_id)).to eq([3])
+      expect(CategoryUser.lookup(user, :watching_first_post).pluck(:category_id)).to eq([4])
     end
 
     it "does not set category preferences for staged users" do
@@ -1286,6 +1288,7 @@ describe User do
       expect(CategoryUser.lookup(user, :watching).pluck(:category_id)).to eq([])
       expect(CategoryUser.lookup(user, :tracking).pluck(:category_id)).to eq([])
       expect(CategoryUser.lookup(user, :muted).pluck(:category_id)).to eq([])
+      expect(CategoryUser.lookup(user, :watching_first_post).pluck(:category_id)).to eq([])
     end
   end