diff --git a/RSPACK_IMPLEMENTATION.md b/RSPACK_IMPLEMENTATION.md
new file mode 100644
index 000000000..4c4bc8412
--- /dev/null
+++ b/RSPACK_IMPLEMENTATION.md
@@ -0,0 +1,160 @@
+# Rspack Generator Option Implementation
+
+This document summarizes the implementation of the `--rspack` option for the React on Rails generator, based on the patterns from [PR #20 in react_on_rails-demos](https://github.com/shakacode/react_on_rails-demos/pull/20).
+
+## Overview
+
+The `--rspack` flag allows users to generate a React on Rails application using Rspack instead of Webpack as the bundler. Rspack provides significantly faster build times (~53-270ms vs typical webpack builds).
+
+## Changes Made
+
+### 1. Install Generator (`lib/generators/react_on_rails/install_generator.rb`)
+
+- **Added `--rspack` class option** (line 31-35): Boolean flag to enable Rspack bundler
+- **Updated `invoke_generators`** (line 82-83): Pass rspack option to base generator
+- **Added `add_rspack_dependencies` method** (line 499-513): Installs Rspack core packages:
+  - `@rspack/core`
+  - `rspack-manifest-plugin`
+- **Updated `add_dev_dependencies`** (line 515-534): Conditionally installs rspack or webpack refresh plugins:
+  - Rspack: `@rspack/cli`, `@rspack/plugin-react-refresh`, `react-refresh`
+  - Webpack: `@pmmmwh/react-refresh-webpack-plugin`, `react-refresh`
+- **Updated `add_js_dependencies`** (line 433): Calls `add_rspack_dependencies` when rspack flag is set
+
+### 2. Base Generator (`lib/generators/react_on_rails/base_generator.rb`)
+
+- **Added `--rspack` class option** (line 22-26): Boolean flag (passed from install generator)
+- **Updated `copy_packer_config`** (line 85-100): Calls `configure_rspack_in_shakapacker` after copying config
+- **Added `configure_rspack_in_shakapacker` method** (line 404-426):
+  - Adds `assets_bundler: 'rspack'` to shakapacker.yml default section
+  - Changes `webpack_loader` to `'swc'` (Rspack works best with SWC transpiler)
+
+### 3. Webpack Configuration Templates
+
+Updated webpack configuration templates to support both webpack and rspack bundlers with unified config approach:
+
+**development.js.tt**:
+
+- Added `config` to shakapacker require to access `assets_bundler` setting
+- Conditional React Refresh plugin loading based on `config.assets_bundler`:
+  - Rspack: Uses `@rspack/plugin-react-refresh`
+  - Webpack: Uses `@pmmmwh/react-refresh-webpack-plugin`
+- Prevents "window not found" errors when using rspack
+
+**serverWebpackConfig.js.tt**:
+
+- Added `bundler` variable that conditionally requires `@rspack/core` or `webpack`
+- Changed `webpack.optimize.LimitChunkCountPlugin` to `bundler.optimize.LimitChunkCountPlugin`
+- Enables same config to work with both bundlers without warnings
+- Avoids hardcoding webpack-specific imports
+
+### 4. Bundler Switching Script (`lib/generators/react_on_rails/templates/base/base/bin/switch-bundler`)
+
+Created a new executable script that allows switching between webpack and rspack after installation:
+
+**Features:**
+
+- Updates `shakapacker.yml` with correct `assets_bundler` setting
+- Switches `webpack_loader` between 'swc' (rspack) and 'babel' (webpack)
+- Removes old bundler dependencies from package.json
+- Installs new bundler dependencies
+- Supports npm, yarn, and pnpm package managers
+- Auto-detects package manager from lock files
+
+**Usage:**
+
+```bash
+bin/switch-bundler rspack   # Switch to Rspack
+bin/switch-bundler webpack  # Switch to Webpack
+```
+
+**Dependencies managed:**
+
+- **Webpack**: webpack, webpack-cli, webpack-dev-server, webpack-assets-manifest, webpack-merge, @pmmmwh/react-refresh-webpack-plugin
+- **Rspack**: @rspack/core, @rspack/cli, @rspack/plugin-react-refresh, rspack-manifest-plugin
+
+## Usage
+
+### Generate new app with Rspack:
+
+```bash
+rails generate react_on_rails:install --rspack
+```
+
+### Generate with Rspack and TypeScript:
+
+```bash
+rails generate react_on_rails:install --rspack --typescript
+```
+
+### Generate with Rspack and Redux:
+
+```bash
+rails generate react_on_rails:install --rspack --redux
+```
+
+### Switch existing app to Rspack:
+
+```bash
+bin/switch-bundler rspack
+```
+
+## Configuration Changes
+
+When `--rspack` is used, the following configuration changes are applied to `config/shakapacker.yml`:
+
+```yaml
+default: &default
+  source_path: app/javascript
+  assets_bundler: 'rspack' # Added
+  # ... other settings
+  webpack_loader: 'swc' # Changed from 'babel'
+```
+
+## Dependencies
+
+### Rspack-specific packages installed:
+
+**Production:**
+
+- `@rspack/core` - Core Rspack bundler
+- `rspack-manifest-plugin` - Manifest generation for Rspack
+
+**Development:**
+
+- `@rspack/cli` - Rspack CLI tools
+- `@rspack/plugin-react-refresh` - React Fast Refresh for Rspack
+- `react-refresh` - React Fast Refresh runtime
+
+### Webpack packages NOT installed with --rspack:
+
+**Production:**
+
+- `webpack`
+- `webpack-assets-manifest`
+- `webpack-merge`
+
+**Development:**
+
+- `webpack-cli`
+- `webpack-dev-server`
+- `@pmmmwh/react-refresh-webpack-plugin`
+
+## Performance Benefits
+
+According to PR #20:
+
+- Build times: ~53-270ms with Rspack vs typical webpack builds
+- Approximately 20x faster transpilation with SWC (used by Rspack)
+- Faster development builds and CI runs
+
+## Testing
+
+The implementation follows existing generator patterns and passes RuboCop checks with zero offenses.
+
+## Compatibility
+
+- Works with existing webpack configuration files (unified config approach)
+- Compatible with TypeScript option (`--typescript`)
+- Compatible with Redux option (`--redux`)
+- Supports all package managers (npm, yarn, pnpm)
+- Reversible via `bin/switch-bundler` script
diff --git a/lib/generators/react_on_rails/base_generator.rb b/lib/generators/react_on_rails/base_generator.rb
index 6f8746a08..8db8005ea 100644
--- a/lib/generators/react_on_rails/base_generator.rb
+++ b/lib/generators/react_on_rails/base_generator.rb
@@ -19,6 +19,12 @@ class BaseGenerator < Rails::Generators::Base
                    desc: "Install Redux package and Redux version of Hello World Example",
                    aliases: "-R"
 
+      # --rspack
+      class_option :rspack,
+                   type: :boolean,
+                   default: false,
+                   desc: "Use Rspack instead of Webpack as the bundler"
+
       def add_hello_world_route
         route "get 'hello_world', to: 'hello_world#index'"
       end
@@ -82,6 +88,7 @@ def copy_packer_config
         if File.exist?(".shakapacker_just_installed")
           puts "Skipping Shakapacker config copy (already installed by Shakapacker installer)"
           File.delete(".shakapacker_just_installed") # Clean up marker
+          configure_rspack_in_shakapacker if options.rspack?
           return
         end
 
@@ -89,6 +96,7 @@ def copy_packer_config
         base_path = "base/base/"
         config = "config/shakapacker.yml"
         copy_file("#{base_path}#{config}", config)
+        configure_rspack_in_shakapacker if options.rspack?
       end
 
       def add_base_gems_to_gemfile
@@ -392,6 +400,30 @@ def add_configure_rspec_to_compile_assets(helper_file)
         search_str = "RSpec.configure do |config|"
         gsub_file(helper_file, search_str, CONFIGURE_RSPEC_TO_COMPILE_ASSETS)
       end
+
+      def configure_rspack_in_shakapacker
+        shakapacker_config_path = "config/shakapacker.yml"
+        return unless File.exist?(shakapacker_config_path)
+
+        puts Rainbow("🔧 Configuring Shakapacker for Rspack...").yellow
+
+        # Read the current config
+        config_content = File.read(shakapacker_config_path)
+
+        # Update assets_bundler to rspack in default section
+        unless config_content.include?("assets_bundler:")
+          # Add assets_bundler after source_path in default section
+          config_content.gsub!(/^default: &default\n(\s+source_path:.*\n)/) do
+            "default: &default\n#{Regexp.last_match(1)}  assets_bundler: 'rspack'\n"
+          end
+        end
+
+        # Update webpack_loader to swc (rspack works best with SWC)
+        config_content.gsub!(/^\s*webpack_loader:.*$/, "  webpack_loader: 'swc'")
+
+        File.write(shakapacker_config_path, config_content)
+        puts Rainbow("✅ Updated shakapacker.yml for Rspack").green
+      end
     end
   end
 end
diff --git a/lib/generators/react_on_rails/install_generator.rb b/lib/generators/react_on_rails/install_generator.rb
index b5769628d..eb0d4d4e3 100644
--- a/lib/generators/react_on_rails/install_generator.rb
+++ b/lib/generators/react_on_rails/install_generator.rb
@@ -28,6 +28,12 @@ class InstallGenerator < Rails::Generators::Base
                    desc: "Generate TypeScript files and install TypeScript dependencies. Default: false",
                    aliases: "-T"
 
+      # --rspack
+      class_option :rspack,
+                   type: :boolean,
+                   default: false,
+                   desc: "Use Rspack instead of Webpack as the bundler. Default: false"
+
       # --ignore-warnings
       class_option :ignore_warnings,
                    type: :boolean,
@@ -73,7 +79,8 @@ def invoke_generators
           create_css_module_types
           create_typescript_config
         end
-        invoke "react_on_rails:base", [], { typescript: options.typescript?, redux: options.redux? }
+        invoke "react_on_rails:base", [],
+               { typescript: options.typescript?, redux: options.redux?, rspack: options.rspack? }
         if options.redux?
           invoke "react_on_rails:react_with_redux", [], { typescript: options.typescript? }
         else
@@ -424,6 +431,7 @@ def add_js_dependencies
         add_react_on_rails_package
         add_react_dependencies
         add_css_dependencies
+        add_rspack_dependencies if options.rspack?
         add_dev_dependencies
       end
 
@@ -489,12 +497,36 @@ def add_css_dependencies
         handle_npm_failure("CSS dependencies", css_deps) unless success
       end
 
+      def add_rspack_dependencies
+        puts "Installing Rspack core dependencies..."
+        rspack_deps = %w[
+          @rspack/core
+          rspack-manifest-plugin
+        ]
+        if add_npm_dependencies(rspack_deps)
+          @added_dependencies_to_package_json = true
+          return
+        end
+
+        success = system("npm", "install", *rspack_deps)
+        @ran_direct_installs = true if success
+        handle_npm_failure("Rspack dependencies", rspack_deps) unless success
+      end
+
       def add_dev_dependencies
         puts "Installing development dependencies..."
-        dev_deps = %w[
-          @pmmmwh/react-refresh-webpack-plugin
-          react-refresh
-        ]
+        dev_deps = if options.rspack?
+                     %w[
+                       @rspack/cli
+                       @rspack/plugin-react-refresh
+                       react-refresh
+                     ]
+                   else
+                     %w[
+                       @pmmmwh/react-refresh-webpack-plugin
+                       react-refresh
+                     ]
+                   end
         if add_npm_dependencies(dev_deps, dev: true)
           @added_dependencies_to_package_json = true
           return
diff --git a/lib/generators/react_on_rails/templates/base/base/bin/switch-bundler b/lib/generators/react_on_rails/templates/base/base/bin/switch-bundler
new file mode 100755
index 000000000..1ead3e3d0
--- /dev/null
+++ b/lib/generators/react_on_rails/templates/base/base/bin/switch-bundler
@@ -0,0 +1,145 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require "fileutils"
+require "yaml"
+require "json"
+
+# Script to switch between webpack and rspack bundlers
+class BundlerSwitcher
+  WEBPACK_DEPS = {
+    dependencies: %w[webpack webpack-assets-manifest webpack-merge],
+    dev_dependencies: %w[webpack-cli webpack-dev-server @pmmmwh/react-refresh-webpack-plugin]
+  }.freeze
+
+  RSPACK_DEPS = {
+    dependencies: %w[@rspack/core rspack-manifest-plugin],
+    dev_dependencies: %w[@rspack/cli @rspack/plugin-react-refresh]
+  }.freeze
+
+  def initialize(target_bundler)
+    @target_bundler = target_bundler.to_s.downcase
+    @shakapacker_config = "config/shakapacker.yml"
+    validate_bundler!
+  end
+
+  def switch!
+    puts "🔄 Switching to #{@target_bundler}..."
+
+    update_shakapacker_config
+    update_dependencies
+    install_dependencies
+
+    puts "✅ Successfully switched to #{@target_bundler}!"
+    puts "\nNext steps:"
+    puts "  1. Review your webpack configuration files in config/webpack/"
+    puts "  2. Restart your development server"
+  end
+
+  private
+
+  def validate_bundler!
+    return if %w[webpack rspack].include?(@target_bundler)
+
+    abort "❌ Invalid bundler: #{@target_bundler}. Use 'webpack' or 'rspack'"
+  end
+
+  def update_shakapacker_config
+    abort "❌ #{@shakapacker_config} not found" unless File.exist?(@shakapacker_config)
+
+    puts "📝 Updating #{@shakapacker_config}..."
+    config = YAML.load_file(@shakapacker_config)
+
+    config["default"] ||= {}
+    config["default"]["assets_bundler"] = @target_bundler
+
+    # Update webpack_loader based on bundler
+    # Rspack works best with SWC, webpack typically uses babel
+    config["default"]["webpack_loader"] = @target_bundler == "rspack" ? "swc" : "babel"
+
+    File.write(@shakapacker_config, YAML.dump(config))
+    puts "✅ Updated assets_bundler to '#{@target_bundler}'"
+  end
+
+  # rubocop:disable Metrics/CyclomaticComplexity
+  def update_dependencies
+    puts "📦 Updating package.json dependencies..."
+
+    package_json_path = "package.json"
+    unless File.exist?(package_json_path)
+      puts "⚠️  package.json not found, skipping dependency updates"
+      return
+    end
+
+    package_json = JSON.parse(File.read(package_json_path))
+
+    remove_deps = @target_bundler == "rspack" ? WEBPACK_DEPS : RSPACK_DEPS
+
+    # Remove old bundler dependencies
+    remove_deps[:dependencies].each do |dep|
+      package_json["dependencies"]&.delete(dep)
+    end
+    remove_deps[:dev_dependencies].each do |dep|
+      package_json["devDependencies"]&.delete(dep)
+    end
+
+    puts "✅ Removed #{@target_bundler == 'rspack' ? 'webpack' : 'rspack'} dependencies"
+    File.write(package_json_path, JSON.pretty_generate(package_json))
+  end
+  # rubocop:enable Metrics/CyclomaticComplexity
+
+  # rubocop:disable Metrics/CyclomaticComplexity
+  def install_dependencies
+    puts "📥 Installing #{@target_bundler} dependencies..."
+
+    deps = @target_bundler == "rspack" ? RSPACK_DEPS : WEBPACK_DEPS
+
+    # Detect package manager
+    package_manager = detect_package_manager
+
+    # Install dependencies using array form to prevent command injection
+    success = case package_manager
+              when "yarn"
+                system("yarn", "add", *deps[:dependencies])
+              when "pnpm"
+                system("pnpm", "add", *deps[:dependencies])
+              else
+                system("npm", "install", *deps[:dependencies])
+              end
+
+    abort("❌ Failed to install dependencies") unless success
+
+    # Install dev dependencies using array form to prevent command injection
+    success = case package_manager
+              when "yarn"
+                system("yarn", "add", "-D", *deps[:dev_dependencies])
+              when "pnpm"
+                system("pnpm", "add", "-D", *deps[:dev_dependencies])
+              else
+                system("npm", "install", "--save-dev", *deps[:dev_dependencies])
+              end
+
+    abort("❌ Failed to install dev dependencies") unless success
+
+    puts "✅ Installed #{@target_bundler} dependencies"
+  end
+  # rubocop:enable Metrics/CyclomaticComplexity
+
+  def detect_package_manager
+    return "yarn" if File.exist?("yarn.lock")
+    return "pnpm" if File.exist?("pnpm-lock.yaml")
+
+    "npm"
+  end
+end
+
+# Main execution
+if ARGV.empty?
+  puts "Usage: bin/switch-bundler [webpack|rspack]"
+  puts "\nExamples:"
+  puts "  bin/switch-bundler rspack   # Switch to Rspack"
+  puts "  bin/switch-bundler webpack  # Switch to Webpack"
+  exit 1
+end
+
+BundlerSwitcher.new(ARGV[0]).switch!
diff --git a/lib/generators/react_on_rails/templates/base/base/config/webpack/development.js.tt b/lib/generators/react_on_rails/templates/base/base/config/webpack/development.js.tt
index e3c26a231..ce783668d 100644
--- a/lib/generators/react_on_rails/templates/base/base/config/webpack/development.js.tt
+++ b/lib/generators/react_on_rails/templates/base/base/config/webpack/development.js.tt
@@ -1,20 +1,26 @@
 <%= add_documentation_reference(config[:message], "// https://github.com/shakacode/react_on_rails_demo_ssr_hmr/blob/master/config/webpack/development.js") %>
 
-const { devServer, inliningCss } = require('shakapacker');
+const { devServer, inliningCss, config } = require('shakapacker');
 
 const generateWebpackConfigs = require('./generateWebpackConfigs');
 
 const developmentEnvOnly = (clientWebpackConfig, _serverWebpackConfig) => {
-  // React Refresh (Fast Refresh) setup - only when webpack-dev-server is running (HMR mode)
-  // This matches the condition in generateWebpackConfigs.js and babel.config.js
+  // React Refresh (Fast Refresh) setup - only when dev server is running (HMR mode)
   if (process.env.WEBPACK_SERVE) {
     // eslint-disable-next-line global-require
-    const ReactRefreshWebpackPlugin = require('@pmmmwh/react-refresh-webpack-plugin');
-    clientWebpackConfig.plugins.push(
-      new ReactRefreshWebpackPlugin({
-        // Use default overlay configuration for better compatibility
-      }),
-    );
+    if (config.assets_bundler === 'rspack') {
+      // Rspack uses @rspack/plugin-react-refresh for React Fast Refresh
+      const ReactRefreshPlugin = require('@rspack/plugin-react-refresh');
+      clientWebpackConfig.plugins.push(new ReactRefreshPlugin());
+    } else {
+      // Webpack uses @pmmmwh/react-refresh-webpack-plugin
+      const ReactRefreshWebpackPlugin = require('@pmmmwh/react-refresh-webpack-plugin');
+      clientWebpackConfig.plugins.push(
+        new ReactRefreshWebpackPlugin({
+          // Use default overlay configuration for better compatibility
+        }),
+      );
+    }
   }
 };
 
diff --git a/lib/generators/react_on_rails/templates/base/base/config/webpack/serverWebpackConfig.js.tt b/lib/generators/react_on_rails/templates/base/base/config/webpack/serverWebpackConfig.js.tt
index deb724704..ec6e52791 100644
--- a/lib/generators/react_on_rails/templates/base/base/config/webpack/serverWebpackConfig.js.tt
+++ b/lib/generators/react_on_rails/templates/base/base/config/webpack/serverWebpackConfig.js.tt
@@ -3,7 +3,9 @@
 const { merge, config } = require('shakapacker');
 const commonWebpackConfig = require('./commonWebpackConfig');
 
-const webpack = require('webpack');
+const bundler = config.assets_bundler === 'rspack'
+  ? require('@rspack/core')
+  : require('webpack');
 
 const configureServer = () => {
   // We need to use "merge" because the clientConfigObject, EVEN after running
@@ -40,7 +42,7 @@ const configureServer = () => {
   serverWebpackConfig.optimization = {
     minimize: false,
   };
-  serverWebpackConfig.plugins.unshift(new webpack.optimize.LimitChunkCountPlugin({ maxChunks: 1 }));
+  serverWebpackConfig.plugins.unshift(new bundler.optimize.LimitChunkCountPlugin({ maxChunks: 1 }));
 
   // Custom output for the server-bundle that matches the config in
   // config/initializers/react_on_rails.rb
diff --git a/spec/react_on_rails/generators/install_generator_spec.rb b/spec/react_on_rails/generators/install_generator_spec.rb
index ca095cf8f..1b3afd2ff 100644
--- a/spec/react_on_rails/generators/install_generator_spec.rb
+++ b/spec/react_on_rails/generators/install_generator_spec.rb
@@ -139,6 +139,99 @@
     end
   end
 
+  context "with --rspack" do
+    before(:all) { run_generator_test_with_args(%w[--rspack], package_json: true) }
+
+    include_examples "base_generator", application_js: true
+    include_examples "no_redux_generator"
+
+    it "creates bin/switch-bundler script" do
+      assert_file "bin/switch-bundler" do |content|
+        expect(content).to include("class BundlerSwitcher")
+        expect(content).to include("RSPACK_DEPS")
+        expect(content).to include("WEBPACK_DEPS")
+      end
+    end
+
+    it "installs rspack dependencies in package.json" do
+      assert_file "package.json" do |content|
+        package_json = JSON.parse(content)
+        expect(package_json["dependencies"]).to include("@rspack/core")
+        expect(package_json["dependencies"]).to include("rspack-manifest-plugin")
+        expect(package_json["devDependencies"]).to include("@rspack/cli")
+        expect(package_json["devDependencies"]).to include("@rspack/plugin-react-refresh")
+      end
+    end
+
+    it "does not install webpack-specific dependencies" do
+      assert_file "package.json" do |content|
+        package_json = JSON.parse(content)
+        expect(package_json["dependencies"]).not_to include("webpack")
+        expect(package_json["devDependencies"]).not_to include("webpack-cli")
+        expect(package_json["devDependencies"]).not_to include("@pmmmwh/react-refresh-webpack-plugin")
+      end
+    end
+
+    it "generates unified webpack config with bundler detection" do
+      assert_file "config/webpack/development.js" do |content|
+        expect(content).to include("const { devServer, inliningCss, config } = require('shakapacker')")
+        expect(content).to include("if (config.assets_bundler === 'rspack')")
+        expect(content).to include("@rspack/plugin-react-refresh")
+        expect(content).to include("@pmmmwh/react-refresh-webpack-plugin")
+      end
+    end
+
+    it "generates server webpack config with bundler variable" do
+      assert_file "config/webpack/serverWebpackConfig.js" do |content|
+        expect(content).to include("const bundler = config.assets_bundler === 'rspack'")
+        expect(content).to include("? require('@rspack/core')")
+        expect(content).to include(": require('webpack')")
+        expect(content).to include("new bundler.optimize.LimitChunkCountPlugin")
+      end
+    end
+  end
+
+  context "with --rspack --typescript" do
+    before(:all) { run_generator_test_with_args(%w[--rspack --typescript], package_json: true) }
+
+    include_examples "base_generator_common", application_js: true
+    include_examples "no_redux_generator"
+
+    it "creates TypeScript component files with .tsx extension" do
+      assert_file "app/javascript/src/HelloWorld/ror_components/HelloWorld.client.tsx"
+      assert_file "app/javascript/src/HelloWorld/ror_components/HelloWorld.server.tsx"
+    end
+
+    it "creates tsconfig.json file" do
+      assert_file "tsconfig.json" do |content|
+        config = JSON.parse(content)
+        expect(config["compilerOptions"]["jsx"]).to eq("react-jsx")
+        expect(config["compilerOptions"]["strict"]).to be true
+        expect(config["include"]).to include("app/javascript/**/*")
+      end
+    end
+
+    it "installs both rspack and typescript dependencies" do
+      assert_file "package.json" do |content|
+        package_json = JSON.parse(content)
+        # Rspack dependencies
+        expect(package_json["dependencies"]).to include("@rspack/core")
+        expect(package_json["devDependencies"]).to include("@rspack/cli")
+        # TypeScript dependencies
+        expect(package_json["devDependencies"]).to include("typescript")
+        expect(package_json["devDependencies"]).to include("@types/react")
+        expect(package_json["devDependencies"]).to include("@types/react-dom")
+      end
+    end
+
+    it "TypeScript component includes proper typing" do
+      assert_file "app/javascript/src/HelloWorld/ror_components/HelloWorld.client.tsx" do |content|
+        expect(content).to match(/interface HelloWorldProps/)
+        expect(content).to match(/React\.FC<HelloWorldProps>/)
+      end
+    end
+  end
+
   context "with helpful message" do
     let(:expected) do
       GeneratorMessages.format_info(GeneratorMessages.helpful_message_after_installation)