diff --git a/Gemfile.lock b/Gemfile.lock
index 41e2abf..2012174 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -188,7 +188,7 @@ GEM
     language_server-protocol (3.17.0.5)
     lint_roller (1.1.0)
     logger (1.7.0)
-    loofah (2.25.1)
+    loofah (2.25.2)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
     mail (2.9.0)
@@ -293,8 +293,8 @@ GEM
       activesupport (>= 5.0.0)
       minitest
       nokogiri (>= 1.6)
-    rails-html-sanitizer (1.7.0)
-      loofah (~> 2.25)
+    rails-html-sanitizer (1.7.1)
+      loofah (~> 2.25, >= 2.25.2)
       nokogiri (>= 1.15.7, != 1.16.7, != 1.16.6, != 1.16.5, != 1.16.4, != 1.16.3, != 1.16.2, != 1.16.1, != 1.16.0.rc1, != 1.16.0)
     railties (8.1.3)
       actionpack (= 8.1.3)
diff --git a/app/controllers/users/registrations_controller.rb b/app/controllers/users/registrations_controller.rb
new file mode 100644
index 0000000..e41a4b0
--- /dev/null
+++ b/app/controllers/users/registrations_controller.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module Users
+  class RegistrationsController < Devise::RegistrationsController
+    # rubocop:disable Rails/LexicallyScopedActionFilter
+    before_action :protect_demo_account!, only: %i[update destroy]
+    # rubocop:enable Rails/LexicallyScopedActionFilter
+
+    private
+
+    def protect_demo_account!
+      return unless current_user&.demo_account?
+
+      redirect_to authenticated_root_path,
+                  alert: t("users.registrations.demo_account_protected")
+    end
+  end
+end
diff --git a/app/models/user.rb b/app/models/user.rb
index 4ce0a9e..9ecf6ac 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -1,6 +1,12 @@
 # frozen_string_literal: true
 
 class User < ApplicationRecord
+  DEMO_EMAIL = "demo@example.com"
+
+  def demo_account?
+    email == DEMO_EMAIL
+  end
+
   devise :database_authenticatable, :registerable,
          :recoverable, :rememberable, :validatable
 
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 3a2948e..1d3d24f 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -52,4 +52,8 @@ en:
       success: "Project successfully deleted."
     index:
       new_project: "New Project"
-      title: "Projects"
\ No newline at end of file
+      title: "Projects"
+  
+  users:
+    registrations:
+      demo_account_protected: "Demo account settings are protected."
\ No newline at end of file
diff --git a/config/routes.rb b/config/routes.rb
index 7f4d388..ccabe30 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -1,7 +1,9 @@
 # frozen_string_literal: true
 
 Rails.application.routes.draw do
-  devise_for :users
+  devise_for :users, controllers: {
+    registrations: "users/registrations"
+  }
 
   authenticated :user do
     root "dashboard#index", as: :authenticated_root
diff --git a/spec/requests/users/registrations_spec.rb b/spec/requests/users/registrations_spec.rb
new file mode 100644
index 0000000..cdfe2db
--- /dev/null
+++ b/spec/requests/users/registrations_spec.rb
@@ -0,0 +1,90 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+RSpec.describe "User registrations" do
+  describe "PATCH /users" do
+    context "when the current user is the demo user" do
+      let(:user) { create(:user, email: User::DEMO_EMAIL) }
+
+      before { sign_in user }
+
+      it "does not update the account" do
+        patch user_registration_path, params: {
+          user: {
+            email: "changed@example.com",
+            current_password: user.password
+          }
+        }
+
+        expect(user.reload.email).to eq(User::DEMO_EMAIL)
+      end
+
+      it "redirects with an alert" do
+        patch user_registration_path, params: {
+          user: {
+            email: "changed@example.com",
+            current_password: user.password
+          }
+        }
+
+        expect(response).to redirect_to(authenticated_root_path)
+        expect(flash[:alert]).to eq(
+          I18n.t("users.registrations.demo_account_protected")
+        )
+      end
+    end
+
+    context "when the current user is not the demo user" do
+      let(:user) { create(:user) }
+
+      before { sign_in user }
+
+      it "allows the account to be updated" do
+        patch user_registration_path, params: {
+          user: {
+            email: "changed@example.com",
+            current_password: user.password
+          }
+        }
+
+        expect(user.reload.email).to eq("changed@example.com")
+      end
+    end
+  end
+
+  describe "DELETE /users" do
+    context "when the current user is the demo user" do
+      let!(:user) { create(:user, email: User::DEMO_EMAIL) }
+
+      before { sign_in user }
+
+      it "does not delete the account" do
+        expect do
+          delete user_registration_path
+        end.not_to change(User, :count)
+      end
+
+      it "redirects with an alert" do
+        delete user_registration_path
+
+        expect(response).to redirect_to(authenticated_root_path)
+        expect(flash[:alert]).to eq(
+          I18n.t("users.registrations.demo_account_protected")
+        )
+      end
+    end
+
+    context "when the current user is not the demo user" do
+      let!(:user) { create(:user) }
+
+      before { sign_in user }
+
+      it "deletes the account" do
+        expect do
+          delete user_registration_path
+        end.to change(User, :count).by(-1)
+      end
+    end
+  end
+end