diff --git a/Gemfile b/Gemfile
index 340c199..118c24d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -67,6 +67,9 @@ gem 'http_accept_language'
 # Routes for JS files
 gem 'js-routes', '~> 1.1.0'
 
+# External logins with OmniAuth
+gem 'omniauth'
+
 group :test do
   # Easier test writing
   gem "shoulda-matchers", '~> 2.8.0'
diff --git a/Gemfile.lock b/Gemfile.lock
index 6839378..0368fed 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -134,6 +134,7 @@ GEM
     globalid (0.3.6)
       activesupport (>= 4.1.0)
     google-analytics-rails (0.0.6)
+    hashie (3.4.1)
     http-cookie (1.0.2)
       domain_name (~> 0.5)
     http_accept_language (2.0.5)
@@ -206,6 +207,9 @@ GEM
     nokogiri (1.6.6.2)
       mini_portile (~> 0.6.0)
     ntlm-http (0.1.1)
+    omniauth (1.2.2)
+      hashie (>= 1.2, < 4)
+      rack (~> 1.0)
     orm_adapter (0.5.0)
     pg (0.18.3)
     poltergeist (1.7.0)
@@ -364,6 +368,7 @@ DEPENDENCIES
   konacha
   less-rails (~> 2.7.0)
   mocha
+  omniauth
   pg (~> 0.18.1)
   poltergeist (~> 1.7.0)
   rails (= 4.2.4)
diff --git a/app/models/user.rb b/app/models/user.rb
index 082e5ce..468fd52 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -2,11 +2,14 @@ class User < ActiveRecord::Base
   # Include default devise modules. Others available are:
   # :token_authenticatable, :confirmable,
   # :lockable, :timeoutable and :omniauthable
-  devise :database_authenticatable, :registerable, :recoverable, :rememberable, :trackable, :validatable
+  devise :database_authenticatable, :registerable, :recoverable, :rememberable, :trackable, :validatable,
+         :omniauthable, omniauth_providers: []
 
   validates :name, presence: true
-  validates :email, presence: true
-  validates :email, uniqueness: true
+  validates :email, presence: true, uniqueness: true
+  validates :provider, presence: true, unless: Proc.new { |user| user.uid.nil? || user.uid.blank? }
+  validates :uid, presence: true, uniqueness: { scope: :provider },
+            unless: Proc.new { |user| user.provider.nil? || user.provider.blank? }
 
   has_many :project_attributes, class_name: 'ProjectAttributes', dependent: :destroy
   has_many :reading_group_attributes, class_name: 'ReadingGroupAttributes', dependent: :destroy
@@ -17,4 +20,10 @@ class User < ActiveRecord::Base
   def projects
     project_attributes.map { |project_attr| project_attr.project }
   end
+
+  protected
+
+  def password_required?
+    provider.nil?
+  end
 end
diff --git a/config/routes.rb b/config/routes.rb
index b4f3b12..65cbc34 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -1,6 +1,7 @@
 Rails.application.routes.draw do
   scope "(:locale)", locale: /en|pt/ do
-    devise_for :users
+    # We need to manually define OmniAuth routes since the automatic generation does not support the dynamic scope
+    devise_for :users, skip: :omniauth_callbacks
     get 'users/:user_id/projects' => 'users#projects', as: :user_projects
 
     resources :projects do
@@ -48,6 +49,9 @@ Rails.application.routes.draw do
     root "home#index"
   end
 
+
+  # See comment above for devise_for
+  devise_for :users, only: :omniauth_callbacks
   # The priority is based upon order of creation: first created -> highest priority.
   # See how all your routes lay out with "rake routes".
 
diff --git a/db/migrate/20150423204406_add_uid_and_provider_to_user.rb b/db/migrate/20150423204406_add_uid_and_provider_to_user.rb
new file mode 100644
index 0000000..7a7164f
--- /dev/null
+++ b/db/migrate/20150423204406_add_uid_and_provider_to_user.rb
@@ -0,0 +1,7 @@
+class AddUidAndProviderToUser < ActiveRecord::Migration
+  def change
+    add_column :users, :uid, :string
+    add_column :users, :provider, :string
+    add_index :users, [:uid, :provider], unique: true
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 365f524..a0eb96a 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -62,9 +62,12 @@ ActiveRecord::Schema.define(version: 20160418192431) do
     t.datetime "last_sign_in_at"
     t.string   "current_sign_in_ip",     limit: 255
     t.string   "last_sign_in_ip",        limit: 255
+    t.string   "uid"
+    t.string   "provider"
   end
 
   add_index "users", ["email"], name: "index_users_on_email", unique: true
   add_index "users", ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
+  add_index "users", ["uid", "provider"], name: "index_users_on_uid_and_provider", unique: true, using: :btree
 
 end
--
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