diff --git a/app/controllers/repositories_controller.rb b/app/controllers/repositories_controller.rb
index a0aab43..f831645 100644
--- a/app/controllers/repositories_controller.rb
+++ b/app/controllers/repositories_controller.rb
@@ -1,7 +1,7 @@
 # app/controllers/repositories_controller.rb
 class RepositoriesController < ApplicationController
   before_action :authenticate_user!
-  before_action :set_user
+  before_action :set_user, except: [ :check_name ]
 
   def index
     @repositories = @user.repositories
@@ -22,6 +22,13 @@ def create
     end
   end
 
+  def check_name
+    validator = GithubRepositoryNameValidator.new(
+      params[:name],
+      current_user.github_username
+    )
+    render json: { available: validator.valid? }
+  end
   private
 
   def set_user
diff --git a/app/javascript/controllers/repository_name_validator_controller.js b/app/javascript/controllers/repository_name_validator_controller.js
new file mode 100644
index 0000000..d81719a
--- /dev/null
+++ b/app/javascript/controllers/repository_name_validator_controller.js
@@ -0,0 +1,90 @@
+import { Controller } from "@hotwired/stimulus"
+
+export default class extends Controller {
+  static targets = ["input", "message", "spinner"]
+  static values = {
+    checkUrl: String,
+    debounce: { type: Number, default: 500 }
+  }
+
+  static classes = ["error", "success"]
+
+  initialize() {
+    this.timeout = null
+    this.debouncedValidate = this.debounce(
+      this.performValidation.bind(this),
+      this.debounceValue
+    )
+  }
+
+  debounce(func, wait) {
+    return (...args) => {
+      clearTimeout(this.timeout)
+      this.timeout = setTimeout(() => func.apply(this, args), wait)
+    }
+  }
+
+  validate() {
+    this.spinnerTarget.classList.remove('hidden')
+    this.messageTarget.classList.add('hidden')
+    this.debouncedValidate()
+  }
+
+  async performValidation() {
+    const name = this.inputTarget.value
+    const valid = this.validateFormat(name)
+
+    this.spinnerTarget.classList.add('hidden')
+
+    if (!valid) {
+      this.showMessage("Invalid format. Use only letters, numbers, and single hyphens.", "error")
+      return
+    }
+
+    try {
+      const available = await this.checkAvailability(name)
+      if (!available) {
+        this.showMessage("Repository name already taken", "error")
+        return
+      }
+      this.showMessage("Name available", "success")
+    } catch (error) {
+      // Error message already shown by checkAvailability
+      return
+    }
+  }
+
+  validateFormat(name) {
+    const regex = /^[a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9]$/
+    return regex.test(name) && !name.includes('--')
+  }
+
+  async checkAvailability(name) {
+    try {
+      const response = await fetch(`${this.checkUrlValue}?name=${encodeURIComponent(name)}`)
+      if (!response.ok) throw new Error('Network response was not ok')
+      const data = await response.json()
+      return data.available
+    } catch (error) {
+      console.error('Error checking availability:', error)
+      this.showMessage("Error checking availability", "error")
+      throw error
+    }
+  }
+
+  showMessage(message, type) {
+    this.messageTarget.textContent = message
+    this.messageTarget.classList.remove("hidden", this.errorClasses, this.successClasses)
+    this.messageTarget.classList.add(type === "error" ? this.errorClasses : this.successClasses)
+  }
+
+  hideMessage() {
+    this.messageTarget.classList.add("hidden")
+  }
+
+  disconnect() {
+    if (this.timeout) {
+      clearTimeout(this.timeout)
+    }
+  }
+}
diff --git a/app/services/github_repository_name_validator.rb b/app/services/github_repository_name_validator.rb
new file mode 100644
index 0000000..44a9177
--- /dev/null
+++ b/app/services/github_repository_name_validator.rb
@@ -0,0 +1,32 @@
+class GithubRepositoryNameValidator
+  VALID_FORMAT = /\A[a-zA-Z0-9][a-zA-Z0-9-]*(?<!-)\z/
+
+  def initialize(name, owner)
+    @name = name.to_s
+    @owner = owner.to_s
+  end
+
+  def valid?
+    valid_format? && double_hyphen_free? && available?
+  end
+
+  private
+
+  def valid_format?
+    @name.match?(VALID_FORMAT)
+  end
+
+  def double_hyphen_free?
+    !@name.include?("--")
+  end
+
+  def available?
+    client = Octokit::Client.new(access_token: ENV["GITHUB_ACCESS_TOKEN"])
+    begin
+      client.repository("#{@owner}/#{@name}")
+      false # Repository exists
+    rescue Octokit::NotFound
+      true # Repository is available
+    end
+  end
+end
diff --git a/app/views/repositories/new.html.erb b/app/views/repositories/new.html.erb
index df0d8d5..12d3cd3 100644
--- a/app/views/repositories/new.html.erb
+++ b/app/views/repositories/new.html.erb
@@ -1,10 +1,28 @@
 <div class="max-w-md mx-auto mt-8">
   <h1 class="text-2xl font-bold mb-4">Create New Repository</h1>
   <%= form_with(model: [ @user, @repository ], class: "space-y-4") do |f| %>
-    <div>
-      <%= f.label :name, class: "block text-sm font-medium text-gray-700" %>
-      <%= f.text_field :name, class: "mt-1 block w-full rounded-md border-gray-300 shadow-sm focus:border-indigo-500 focus:ring-indigo-500" %>
-    </div>
-    <%= f.submit "Create Repository", class: "w-full flex justify-center py-2 px-4 border border-transparent rounded-md shadow-sm text-sm font-medium text-white bg-indigo-600 hover:bg-indigo-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500" %>
-  <% end %>
-</div>
+    <div data-controller="repository-name-validator"
+       data-repository-name-validator-check-url-value="<%= repositories_check_name_path %>"
+     data-repository-name-validator-debounce-value="500"
+     data-repository-name-validator-error-class="text-red-600"
+     data-repository-name-validator-success-class="text-green-600">
+        <%= f.label :name, class: "block text-sm font-medium text-gray-700" %>
+        <%= f.text_field :name,
+          class: "mt-1 block w-full rounded-md border-gray-300 shadow-sm focus:border-indigo-500 focus:ring-indigo-500 sm:text-sm",
+          data: {
+            repository_name_validator_target: "input",
+        action: "input->repository-name-validator#validate"
+        } %>
+        <div class="mt-2 text-sm">
+          <div data-repository-name-validator-target="message" class="hidden"></div>
+          <div data-repository-name-validator-target="spinner" class="hidden flex justify-center">
+            <svg class="animate-spin h-5 w-5 text-gray-500" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24">
+              <circle class="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" stroke-width="4"></circle>
+              <path class="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4zm2 5.291A7.962 7.962 0 014 12H0c0 3.042 1.135 5.824 3 7.938l3-2.647z"></path>
+            </svg>
+          </div>
+        </div>
+      </div>
+      <%= f.submit "Create Repository", class: "w-full flex justify-center py-2 px-4 border border-transparent rounded-md shadow-sm text-sm font-medium text-white bg-indigo-600 hover:bg-indigo-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500" %>
+    <% end %>
+  </div>
diff --git a/config/routes.rb b/config/routes.rb
index 326698f..336f6a9 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -25,4 +25,6 @@
   end
 
   root to: "static#home"
+
+  get "/repositories/check_name", to: "repositories#check_name"
 end
diff --git a/test/services/github_repository_name_validator_test.rb b/test/services/github_repository_name_validator_test.rb
new file mode 100644
index 0000000..5e0494a
--- /dev/null
+++ b/test/services/github_repository_name_validator_test.rb
@@ -0,0 +1,64 @@
+require "test_helper"
+
+class GithubRepositoryNameValidatorTest < ActiveSupport::TestCase
+  def setup
+    @owner = "test-owner"
+  end
+
+  def test_valid_repository_name
+    client = Minitest::Mock.new
+    client.expect(:repository, nil) { raise Octokit::NotFound }
+
+    Octokit::Client.stub(:new, client) do
+      validator = GithubRepositoryNameValidator.new("valid-repo-name", @owner)
+      assert validator.valid?
+    end
+  end
+
+  def test_invalid_ending_with_hyphen
+    validator = GithubRepositoryNameValidator.new("invalid-", @owner)
+    assert_not validator.valid?
+  end
+
+  def test_invalid_starting_with_hyphen
+    validator = GithubRepositoryNameValidator.new("-invalid", @owner)
+    assert_not validator.valid?
+  end
+
+  def test_invalid_double_hyphen
+    validator = GithubRepositoryNameValidator.new("invalid--name", @owner)
+    assert_not validator.valid?
+  end
+
+  def test_invalid_empty_string
+    validator = GithubRepositoryNameValidator.new("", @owner)
+    assert_not validator.valid?
+  end
+
+  def test_invalid_special_characters
+    validator = GithubRepositoryNameValidator.new("inv@lid", @owner)
+    assert_not validator.valid?
+  end
+
+  def test_invalid_when_repository_exists
+    client = Minitest::Mock.new
+    client.expect(:repository, true, [ "#{@owner}/existing-repo" ])
+
+    Octokit::Client.stub(:new, client) do
+      validator = GithubRepositoryNameValidator.new("existing-repo", @owner)
+      assert_not validator.valid?
+    end
+
+    assert_mock client
+  end
+
+  def test_invalid_with_nil_name
+    client = Minitest::Mock.new
+    client.expect(:repository, nil) { raise Octokit::NotFound }
+
+    Octokit::Client.stub(:new, client) do
+      validator = GithubRepositoryNameValidator.new(nil, @owner)
+      assert_not validator.valid?
+    end
+  end
+end