diff --git a/Gemfile b/Gemfile
index ab62929..5ef7b55 100644
--- a/Gemfile
+++ b/Gemfile
@@ -18,7 +18,7 @@ gem "stimulus-rails"
 gem "jbuilder"
 
 # Use Active Model has_secure_password [https://guides.rubyonrails.org/active_model_basics.html#securepassword]
-# gem "bcrypt", "~> 3.1.7"
+gem "bcrypt", "~> 3.1.7"
 
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
 gem "tzinfo-data", platforms: %i[ windows jruby ]
diff --git a/Gemfile.lock b/Gemfile.lock
index a06cecd..502709a 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -104,6 +104,7 @@ GEM
       public_suffix (>= 2.0.2, < 7.0)
     ast (2.4.2)
     base64 (0.2.0)
+    bcrypt (3.1.20)
     bcrypt_pbkdf (1.1.1)
     bcrypt_pbkdf (1.1.1-arm64-darwin)
     bcrypt_pbkdf (1.1.1-x86_64-darwin)
@@ -367,6 +368,7 @@ PLATFORMS
   x86_64-linux-musl
 
 DEPENDENCIES
+  bcrypt (~> 3.1.7)
   bootsnap
   brakeman
   capybara
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 0d95db2..94e7183 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -1,4 +1,5 @@
 class ApplicationController < ActionController::Base
+  include Authentication
   # Only allow modern browsers supporting webp images, web push, badges, import maps, CSS nesting, and CSS :has.
   allow_browser versions: :modern
 end
diff --git a/app/controllers/concerns/authentication.rb b/app/controllers/concerns/authentication.rb
new file mode 100644
index 0000000..c4921f1
--- /dev/null
+++ b/app/controllers/concerns/authentication.rb
@@ -0,0 +1,55 @@
+module Authentication
+  extend ActiveSupport::Concern
+
+  included do
+    before_action :require_authentication
+    helper_method :authenticated?
+  end
+
+  class_methods do
+    def allow_unauthenticated_access(**options)
+      skip_before_action :require_authentication, **options
+    end
+  end
+
+  private
+    def authenticated?
+      Current.session.present?
+    end
+
+    def require_authentication
+      resume_session || request_authentication
+    end
+
+
+    def resume_session
+      Current.session = find_session_by_cookie
+    end
+
+    def find_session_by_cookie
+      Session.find_by(id: cookies.signed[:session_id])
+    end
+
+
+    def request_authentication
+      session[:return_to_after_authenticating] = request.url
+      redirect_to new_session_url
+    end
+
+    def after_authentication_url
+      session.delete(:return_to_after_authenticating) || root_url
+    end
+
+
+    def start_new_session_for(user)
+      user.sessions.create!(user_agent: request.user_agent, ip_address: request.remote_ip).tap do |session|
+        Current.session = session
+        cookies.signed.permanent[:session_id] = { value: session.id, httponly: true, same_site: :lax }
+      end
+    end
+
+    def terminate_session
+      Current.session.destroy
+      cookies.delete(:session_id)
+    end
+end
diff --git a/app/controllers/passwords_controller.rb b/app/controllers/passwords_controller.rb
new file mode 100644
index 0000000..9c6e2b3
--- /dev/null
+++ b/app/controllers/passwords_controller.rb
@@ -0,0 +1,33 @@
+class PasswordsController < ApplicationController
+  allow_unauthenticated_access
+  before_action :set_user_by_token, only: %i[ edit update ]
+
+  def new
+  end
+
+  def create
+    if user = User.find_by(email_address: params[:email_address])
+      PasswordsMailer.reset(user).deliver_later
+    end
+
+    redirect_to new_session_url, notice: "Password reset instructions sent (if user with that email address exists)."
+  end
+
+  def edit
+  end
+
+  def update
+    if @user.update(params.permit(:password, :password_confirmation))
+      redirect_to new_session_url, notice: "Password has been reset."
+    else
+      redirect_to edit_password_url(params[:token]), alert: "Passwords did not match."
+    end
+  end
+
+  private
+    def set_user_by_token
+      @user = User.find_by_password_reset_token!(params[:token])
+    rescue ActiveSupport::MessageVerifier::InvalidSignature
+      redirect_to new_password_url, alert: "Password reset link is invalid or has expired."
+    end
+end
diff --git a/app/controllers/sessions_controller.rb b/app/controllers/sessions_controller.rb
new file mode 100644
index 0000000..b50f0b2
--- /dev/null
+++ b/app/controllers/sessions_controller.rb
@@ -0,0 +1,21 @@
+class SessionsController < ApplicationController
+  allow_unauthenticated_access only: %i[ new create ]
+  rate_limit to: 10, within: 3.minutes, only: :create, with: -> { redirect_to new_session_url, alert: "Try again later." }
+
+  def new
+  end
+
+  def create
+    if user = User.authenticate_by(params.permit(:email_address, :password))
+      start_new_session_for user
+      redirect_to after_authentication_url
+    else
+      redirect_to new_session_url, alert: "Try another email address or password."
+    end
+  end
+
+  def destroy
+    terminate_session
+    redirect_to new_session_url
+  end
+end
diff --git a/app/mailers/passwords_mailer.rb b/app/mailers/passwords_mailer.rb
new file mode 100644
index 0000000..4f0ac7f
--- /dev/null
+++ b/app/mailers/passwords_mailer.rb
@@ -0,0 +1,6 @@
+class PasswordsMailer < ApplicationMailer
+  def reset(user)
+    @user = user
+    mail subject: "Reset your password", to: user.email_address
+  end
+end
diff --git a/app/models/current.rb b/app/models/current.rb
new file mode 100644
index 0000000..2bef56d
--- /dev/null
+++ b/app/models/current.rb
@@ -0,0 +1,4 @@
+class Current < ActiveSupport::CurrentAttributes
+  attribute :session
+  delegate :user, to: :session, allow_nil: true
+end
diff --git a/app/models/session.rb b/app/models/session.rb
new file mode 100644
index 0000000..cf376fb
--- /dev/null
+++ b/app/models/session.rb
@@ -0,0 +1,3 @@
+class Session < ApplicationRecord
+  belongs_to :user
+end
diff --git a/app/models/user.rb b/app/models/user.rb
new file mode 100644
index 0000000..626edbc
--- /dev/null
+++ b/app/models/user.rb
@@ -0,0 +1,6 @@
+class User < ApplicationRecord
+  has_secure_password
+  has_many :sessions, dependent: :destroy
+
+  normalizes :email_address, with: -> e { e.strip.downcase }
+end
diff --git a/app/views/passwords/edit.html.erb b/app/views/passwords/edit.html.erb
new file mode 100644
index 0000000..9f0c87c
--- /dev/null
+++ b/app/views/passwords/edit.html.erb
@@ -0,0 +1,9 @@
+<h1>Update your password</h1>
+
+<%= tag.div(flash[:alert], style: "color:red") if flash[:alert] %>
+
+<%= form_with url: password_path(params[:token]), method: :put do |form| %>
+  <%= form.password_field :password, required: true, autocomplete: "new-password", placeholder: "Enter new password", maxlength: 72 %><br>
+  <%= form.password_field :password_confirmation, required: true, autocomplete: "new-password", placeholder: "Repeat new password", maxlength: 72 %><br>
+  <%= form.submit "Save" %>
+<% end %>
diff --git a/app/views/passwords/new.html.erb b/app/views/passwords/new.html.erb
new file mode 100644
index 0000000..44efb2b
--- /dev/null
+++ b/app/views/passwords/new.html.erb
@@ -0,0 +1,8 @@
+<h1>Forgot your password?</h1>
+
+<%= tag.div(flash[:alert], style: "color:red") if flash[:alert] %>
+
+<%= form_with url: passwords_path do |form| %>
+  <%= form.email_field :email_address, required: true, autofocus: true, autocomplete: "username", placeholder: "Enter your email address", value: params[:email_address] %><br>
+  <%= form.submit "Email reset instructions" %>
+<% end %>
diff --git a/app/views/passwords_mailer/reset.html.erb b/app/views/passwords_mailer/reset.html.erb
new file mode 100644
index 0000000..4a06619
--- /dev/null
+++ b/app/views/passwords_mailer/reset.html.erb
@@ -0,0 +1,4 @@
+<p>
+  You can reset your password within the next 15 minutes on
+  <%= link_to "this password reset page", edit_password_url(@user.password_reset_token) %>.
+</p>
diff --git a/app/views/passwords_mailer/reset.text.erb b/app/views/passwords_mailer/reset.text.erb
new file mode 100644
index 0000000..2cf03fc
--- /dev/null
+++ b/app/views/passwords_mailer/reset.text.erb
@@ -0,0 +1,2 @@
+You can reset your password within the next 15 minutes on this password reset page:
+<%= edit_password_url(@user.password_reset_token) %>
diff --git a/app/views/sessions/new.html.erb b/app/views/sessions/new.html.erb
new file mode 100644
index 0000000..ff641c4
--- /dev/null
+++ b/app/views/sessions/new.html.erb
@@ -0,0 +1,11 @@
+<%= tag.div(flash[:alert], style: "color:red") if flash[:alert] %>
+<%= tag.div(flash[:notice], style: "color:green") if flash[:notice] %>
+
+<%= form_with url: session_path do |form| %>
+  <%= form.email_field :email_address, required: true, autofocus: true, autocomplete: "username", placeholder: "Enter your email address", value: params[:email_address] %><br>
+  <%= form.password_field :password, required: true, autocomplete: "current-password", placeholder: "Enter your password", maxlength: 72 %><br>
+  <%= form.submit "Sign in" %>
+<% end %>
+<br>
+
+<%= link_to "Forgot password?", new_password_path %>
diff --git a/config/routes.rb b/config/routes.rb
index 48254e8..29b007b 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -1,4 +1,6 @@
 Rails.application.routes.draw do
+  resource :session
+  resources :passwords, param: :token
   # Define your application routes per the DSL in https://guides.rubyonrails.org/routing.html
 
   # Reveal health status on /up that returns 200 if the app boots with no exceptions, otherwise 500.
diff --git a/db/migrate/20240928171644_create_users.rb b/db/migrate/20240928171644_create_users.rb
new file mode 100644
index 0000000..2075edf
--- /dev/null
+++ b/db/migrate/20240928171644_create_users.rb
@@ -0,0 +1,11 @@
+class CreateUsers < ActiveRecord::Migration[8.0]
+  def change
+    create_table :users do |t|
+      t.string :email_address, null: false
+      t.string :password_digest, null: false
+
+      t.timestamps
+    end
+    add_index :users, :email_address, unique: true
+  end
+end
diff --git a/db/migrate/20240928171645_create_sessions.rb b/db/migrate/20240928171645_create_sessions.rb
new file mode 100644
index 0000000..8102f13
--- /dev/null
+++ b/db/migrate/20240928171645_create_sessions.rb
@@ -0,0 +1,11 @@
+class CreateSessions < ActiveRecord::Migration[8.0]
+  def change
+    create_table :sessions do |t|
+      t.references :user, null: false, foreign_key: true
+      t.string :ip_address
+      t.string :user_agent
+
+      t.timestamps
+    end
+  end
+end
diff --git a/test/mailers/previews/passwords_mailer_preview.rb b/test/mailers/previews/passwords_mailer_preview.rb
new file mode 100644
index 0000000..01d07ec
--- /dev/null
+++ b/test/mailers/previews/passwords_mailer_preview.rb
@@ -0,0 +1,7 @@
+# Preview all emails at http://localhost:3000/rails/mailers/passwords_mailer
+class PasswordsMailerPreview < ActionMailer::Preview
+  # Preview this email at http://localhost:3000/rails/mailers/passwords_mailer/reset
+  def reset
+    PasswordsMailer.reset(User.take)
+  end
+end