diff --git a/app/models/member.rb b/app/models/member.rb
index d92e69b2ce6..ec79f531740 100644
--- a/app/models/member.rb
+++ b/app/models/member.rb
@@ -26,16 +26,94 @@ class Member < ActiveRecord::Base
   belongs_to :user
   belongs_to :source, polymorphic: true
 
-  validates :user, presence: true
+  validates :user, presence: true, unless: :invite?
   validates :source, presence: true
-  validates :user_id, uniqueness: { scope: [:source_type, :source_id], message: "already exists in source" }
+  validates :user_id, uniqueness: { scope: [:source_type, :source_id], 
+                                    message: "already exists in source",
+                                    allow_nil: true }
   validates :access_level, inclusion: { in: Gitlab::Access.all_values }, presence: true
+  validates :invite_email,  presence: { if: :invite? }, 
+                            email: { strict_mode: true, allow_nil: true }, 
+                            uniqueness: { scope: [:source_type, :source_id], allow_nil: true }
 
+  scope :invite, -> { where(user_id: nil) }
+  scope :non_invite, -> { where("user_id IS NOT NULL") }
   scope :guests, -> { where(access_level: GUEST) }
   scope :reporters, -> { where(access_level: REPORTER) }
   scope :developers, -> { where(access_level: DEVELOPER) }
   scope :masters,  -> { where(access_level: MASTER) }
   scope :owners,  -> { where(access_level: OWNER) }
 
+  before_validation :generate_invite_token, on: :create, if: -> (member) { member.invite_email.present? }
+  after_create :send_invite, if: :invite?
+  after_create :post_create_hook, unless: :invite?
+  after_update :post_update_hook, unless: :invite?
+  after_destroy :post_destroy_hook, unless: :invite?
+
   delegate :name, :username, :email, to: :user, prefix: true
+
+  def invite?
+    self.invite_token.present?
+  end
+
+  def accept_invite!(new_user)
+    self.invite_token = nil
+    self.invite_accepted_at = Time.now.utc
+
+    self.user = new_user
+
+    saved = self.save
+
+    after_accept_invite if saved
+
+    saved
+  end
+
+  def generate_invite_token
+    raw, enc = Devise.token_generator.generate(self.class, :invite_token)
+    @raw_invite_token = raw
+    self.invite_token = enc
+  end
+
+  def generate_invite_token!
+    generate_invite_token && save(validate: false)
+  end
+
+  def resend_invite
+    return unless invite?
+
+    generate_invite_token! unless @raw_invite_token
+
+    send_invite
+  end
+
+  private
+
+  def send_invite
+    # override in subclass
+  end
+
+  def post_create_hook
+    system_hook_service.execute_hooks_for(self, :create)
+  end
+
+  def post_update_hook
+    # override in subclass
+  end
+
+  def post_destroy_hook
+    system_hook_service.execute_hooks_for(self, :destroy)
+  end
+
+  def after_accept_invite
+    post_create_hook
+  end
+
+  def system_hook_service
+    SystemHooksService.new
+  end
+
+  def notification_service
+    NotificationService.new
+  end
 end
diff --git a/app/models/members/group_member.rb b/app/models/members/group_member.rb
index 28d0b4483b4..ccbbab6afc5 100644
--- a/app/models/members/group_member.rb
+++ b/app/models/members/group_member.rb
@@ -27,10 +27,6 @@ class GroupMember < Member
   scope :with_group, ->(group) { where(source_id: group.id) }
   scope :with_user, ->(user) { where(user_id: user.id) }
 
-  after_create :post_create_hook
-  after_update :notify_update
-  after_destroy :post_destroy_hook
-
   def self.access_level_roles
     Gitlab::Access.options_with_owner
   end
@@ -43,26 +39,19 @@ class GroupMember < Member
     access_level
   end
 
+  private
+
   def post_create_hook
     notification_service.new_group_member(self)
-    system_hook_service.execute_hooks_for(self, :create)
+
+    super
   end
 
-  def notify_update
+  def post_update_hook
     if access_level_changed?
       notification_service.update_group_member(self)
     end
-  end
 
-  def post_destroy_hook
-    system_hook_service.execute_hooks_for(self, :destroy)
-  end
-
-  def system_hook_service
-    SystemHooksService.new
-  end
-
-  def notification_service
-    NotificationService.new
+    super
   end
 end
diff --git a/app/models/members/project_member.rb b/app/models/members/project_member.rb
index 2205041cd51..6c5d161940d 100644
--- a/app/models/members/project_member.rb
+++ b/app/models/members/project_member.rb
@@ -27,10 +27,6 @@ class ProjectMember < Member
   validates_format_of :source_type, with: /\AProject\z/
   default_scope { where(source_type: SOURCE_TYPE) }
 
-  after_create :post_create_hook
-  after_update :post_update_hook
-  after_destroy :post_destroy_hook
-
   scope :in_project, ->(project) { where(source_id: project.id) }
   scope :in_projects, ->(projects) { where(source_id: projects.pluck(:id)) }
   scope :with_user, ->(user) { where(user_id: user.id) }
@@ -110,41 +106,40 @@ class ProjectMember < Member
     access_level
   end
 
+  def project
+    source
+  end
+
   def owner?
     project.owner == user
   end
 
+  private
+
   def post_create_hook
     unless owner?
       event_service.join_project(self.project, self.user)
       notification_service.new_project_member(self)
     end
     
-    system_hook_service.execute_hooks_for(self, :create)
+    super
   end
 
   def post_update_hook
-    notification_service.update_project_member(self) if self.access_level_changed?
+    if access_level_changed?
+      notification_service.update_project_member(self) 
+    end
+
+    super
   end
 
   def post_destroy_hook
     event_service.leave_project(self.project, self.user)
-    system_hook_service.execute_hooks_for(self, :destroy)
+
+    super
   end
 
   def event_service
     EventCreateService.new
   end
-
-  def notification_service
-    NotificationService.new
-  end
-
-  def system_hook_service
-    SystemHooksService.new
-  end
-
-  def project
-    source
-  end
 end
diff --git a/spec/models/members_spec.rb b/spec/models/members_spec.rb
index dfd3f7feb6b..3f14a111443 100644
--- a/spec/models/members_spec.rb
+++ b/spec/models/members_spec.rb
@@ -11,10 +11,89 @@ describe Member do
     it { is_expected.to validate_presence_of(:user) }
     it { is_expected.to validate_presence_of(:source) }
     it { is_expected.to validate_inclusion_of(:access_level).in_array(Gitlab::Access.values) }
+
+    context "when an invite email is provided" do
+
+      let(:member) { build(:project_member, invite_email: "user@example.com", user: nil) }
+
+      it "doesn't require a user" do
+        expect(member).to be_valid
+      end
+
+      it "requires a valid invite email" do
+        member.invite_email = "nope"
+
+        expect(member).not_to be_valid
+      end
+
+      it "requires a unique invite email scoped to this source" do
+        create(:project_member, source: member.source, invite_email: member.invite_email)
+
+        expect(member).not_to be_valid
+      end
+
+      it "is valid otherwise" do
+        expect(member).to be_valid
+      end
+    end
+
+    context "when an invite email is not provided" do
+
+      let(:member) { build(:project_member) }
+
+      it "requires a user" do
+        member.user = nil
+
+        expect(member).not_to be_valid
+      end
+
+      it "is valid otherwise" do
+        expect(member).to be_valid
+      end
+    end
   end
 
   describe "Delegate methods" do
     it { is_expected.to respond_to(:user_name) }
     it { is_expected.to respond_to(:user_email) }
   end
+
+  describe "#accept_invite!" do
+
+    let!(:member) { create(:project_member, invite_email: "user@example.com", user: nil) }
+    let(:user) { create(:user) }
+
+    it "resets the invite token" do
+      member.accept_invite!(user)
+
+      expect(member.invite_token).to be_nil
+    end
+
+    it "sets the invite accepted timestamp" do
+      member.accept_invite!(user)
+
+      expect(member.invite_accepted_at).not_to be_nil
+    end
+
+    it "sets the user" do
+      member.accept_invite!(user)
+
+      expect(member.user).to eq(user)
+    end
+
+    it "calls #after_accept_invite" do
+      expect(member).to receive(:after_accept_invite)
+
+      member.accept_invite!(user)
+    end
+  end
+
+  describe "#generate_invite_token" do
+
+    let!(:member) { create(:project_member, invite_email: "user@example.com", user: nil) }
+    
+    it "sets the invite token" do
+      expect { member.generate_invite_token }.to change { member.invite_token}
+    end
+  end
 end