diff --git a/app/controllers/help_controller.rb b/app/controllers/help_controller.rb
index 766781afe..418251172 100644
--- a/app/controllers/help_controller.rb
+++ b/app/controllers/help_controller.rb
@@ -19,18 +19,25 @@
 
 class HelpController < ApplicationController
   def show_wiki_syntax
-    type = params[:type].nil? ? "" : "#{params[:type]}_"
-
-    lang = current_language.to_s
-    template = "help/wiki_syntax/#{Setting.text_formatting}/#{lang}/wiki_syntax_#{type}#{Setting.text_formatting}"
-    unless lookup_context.exists?(template)
-      lang = "en"
-    end
-    render template: "help/wiki_syntax/#{Setting.text_formatting}/#{lang}/wiki_syntax_#{type}#{Setting.text_formatting}", layout: nil
+    render template: wiki_syntax_template_for(params[:type]), layout: nil
   end
 
   def show_code_highlighting
     @available_lexers = Rouge::Lexer.all.sort_by(&:tag)
     render template: "help/wiki_syntax/code_highlighting_languages", layout: nil
   end
+
+  private
+
+  def wiki_syntax_template_for(type)
+    # Region subtags are typically uppercase in locale tags (e.g., ta-IN),
+    # but some help templates use lowercase locale directories, so try both.
+    candidates = [current_language.to_s, current_language.to_s.downcase, "en"].uniq
+    template_name = "wiki_syntax_#{type.present? ? "#{type}_" : ""}#{Setting.text_formatting}"
+
+    candidates.each do |lang|
+      template = "help/wiki_syntax/#{Setting.text_formatting}/#{lang}/#{template_name}"
+      return template if lookup_context.exists?(template)
+    end
+  end
 end
diff --git a/test/functional/help_controller_test.rb b/test/functional/help_controller_test.rb
index c91cc4bda..c87f213e2 100644
--- a/test/functional/help_controller_test.rb
+++ b/test/functional/help_controller_test.rb
@@ -66,13 +66,29 @@ class HelpControllerTest < Redmine::ControllerTest
     assert_select 'h1', :text => "Wiki Syntax Schnellreferenz (CommonMark Markdown (GitHub Flavored))"
   end
 
+  def test_get_help_wiki_syntax_should_fallback_to_lowercase_region_locale_directory
+    user = User.find(2)
+    user.language = 'ta-IN'
+    user.save!
+    @request.session[:user_id] = 2
+
+    with_settings :text_formatting => 'common_mark' do
+      get :show_wiki_syntax
+    end
+    assert_response :success
+
+    assert_select 'h1', :text => "விக்கி தொடரியல் விரைவு குறிப்பு (CommonMark Markdown (GitHub Flavored))"
+  end
+
   def test_get_help_wiki_syntax_should_fallback_to_english
     user = User.find(2)
     user.language = 'ro'
     user.save!
     @request.session[:user_id] = 2
 
-    get :show_wiki_syntax
+    with_settings :text_formatting => 'common_mark' do
+      get :show_wiki_syntax
+    end
     assert_response :success
 
     assert_select 'h1', :text => "Wiki Syntax Quick Reference (CommonMark Markdown (GitHub Flavored))"