diff --git a/app/assets/javascripts/discourse/controllers/invite-private.js.es6 b/app/assets/javascripts/discourse/controllers/invite-private.js.es6
deleted file mode 100644
index 94e1d6632de..00000000000
--- a/app/assets/javascripts/discourse/controllers/invite-private.js.es6
+++ /dev/null
@@ -1,47 +0,0 @@
-import ModalFunctionality from 'discourse/mixins/modal-functionality';
-import ObjectController from 'discourse/controllers/object';
-
-export default ObjectController.extend(ModalFunctionality, {
-  modalClass: 'invite',
-
-  isAdmin: function(){
-    return Discourse.User.currentProp("admin");
-  }.property(),
-
-  onShow: function(){
-    this.set('controllers.modal.modalClass', 'invite-modal');
-    this.set('emailOrUsername', '');
-  },
-
-  disabled: function() {
-    if (this.get('saving')) return true;
-    return this.blank('emailOrUsername');
-  }.property('emailOrUsername', 'saving'),
-
-  buttonTitle: function() {
-    if (this.get('saving')) return I18n.t('topic.inviting');
-    return I18n.t('topic.invite_private.action');
-  }.property('saving'),
-
-  actions: {
-    invite: function() {
-      if (this.get('disabled')) return;
-
-      var self = this;
-      this.setProperties({saving: true, error: false});
-
-      // Invite the user to the private message
-      this.get('model').createInvite(this.get('emailOrUsername')).then(function(result) {
-        self.setProperties({saving: true, finished: true});
-
-        if(result && result.user) {
-          self.get('model.details.allowed_users').pushObject(result.user);
-        }
-      }).catch(function() {
-        self.setProperties({error: true, saving: false});
-      });
-      return false;
-    }
-  }
-
-});
diff --git a/app/assets/javascripts/discourse/controllers/invite.js.es6 b/app/assets/javascripts/discourse/controllers/invite.js.es6
index 6adc0f02081..ad595bb4c46 100644
--- a/app/assets/javascripts/discourse/controllers/invite.js.es6
+++ b/app/assets/javascripts/discourse/controllers/invite.js.es6
@@ -6,7 +6,7 @@ export default ObjectController.extend(ModalFunctionality, {
 
   // If this isn't defined, it will proxy to the user model on the preferences
   // page which is wrong.
-  email: null,
+  emailOrUsername: null,
 
   isAdmin: function(){
     return Discourse.User.currentProp("admin");
@@ -19,12 +19,12 @@ export default ObjectController.extend(ModalFunctionality, {
   **/
   disabled: function() {
     if (this.get('saving')) return true;
-    if (this.blank('email')) return true;
-    if (!Discourse.Utilities.emailValid(this.get('email'))) return true;
+    if (this.blank('emailOrUsername')) return true;
+    if ( !this.get('invitingToTopic') && !Discourse.Utilities.emailValid(this.get('emailOrUsername')) ) return true;
     if (this.get('model.details.can_invite_to')) return false;
     if (this.get('isPrivateTopic') && this.blank('groupNames')) return true;
     return false;
-  }.property('email', 'isPrivateTopic', 'groupNames', 'saving'),
+  }.property('emailOrUsername', 'invitingToTopic', 'isPrivateTopic', 'groupNames', 'saving'),
 
   /**
     The current text for the invite button
@@ -53,18 +53,45 @@ export default ObjectController.extend(ModalFunctionality, {
   **/
   isPrivateTopic: Em.computed.and('invitingToTopic', 'model.category.read_restricted'),
 
+  /**
+    Is Message?
+
+    @property isMessage
+  **/
+  isMessage: Em.computed.equal('model.archetype', 'private_message'),
+
+  /**
+    Allow Existing Members? (username autocomplete)
+
+    @property allowExistingMembers
+  **/
+  allowExistingMembers: function() {
+    return this.get('invitingToTopic') && !this.get('isPrivateTopic');
+  }.property('invitingToTopic', 'isPrivateTopic'),
+
+  /**
+    Show Groups? (add invited user to private group)
+
+    @property showGroups
+  **/
+  showGroups: function() {
+    return this.get('isAdmin') && (Discourse.Utilities.emailValid(this.get('emailOrUsername')) || this.get('isPrivateTopic') || !this.get('invitingToTopic'));
+  }.property('isAdmin', 'emailOrUsername', 'isPrivateTopic', 'invitingToTopic'),
+
   /**
     Instructional text for the modal.
 
     @property inviteInstructions
   **/
   inviteInstructions: function() {
-    if (this.get('invitingToTopic')) {
+    if (this.get('isMessage')) {
+      return I18n.t('topic.invite_private.email_or_username');
+    } else if (this.get('invitingToTopic')) {
       return I18n.t('topic.invite_reply.to_topic');
     } else {
       return I18n.t('topic.invite_reply.to_forum');
     }
-  }.property('invitingToTopic'),
+  }.property('isMessage', 'invitingToTopic'),
 
   /**
     Instructional text for the group selection.
@@ -92,8 +119,25 @@ export default ObjectController.extend(ModalFunctionality, {
     @property successMessage
   **/
   successMessage: function() {
-    return I18n.t('topic.invite_reply.success', { email: this.get('email') });
-  }.property('email'),
+    if (this.get('isMessage')) {
+      return I18n.t('topic.invite_private.success');
+    } else {
+      return I18n.t('topic.invite_reply.success', { emailOrUsername: this.get('emailOrUsername') });
+    }
+  }.property('isMessage', 'emailOrUsername'),
+
+  /**
+    The "error" text for when the invite fails.
+
+    @property errorMessage
+  **/
+  errorMessage: function() {
+    if (this.get('isMessage')) {
+      return I18n.t('topic.invite_private.error');
+    } else {
+      return I18n.t('topic.invite_reply.error');
+    }
+  }.property('isMessage'),
 
   /**
     Reset the modal to allow a new user to be invited.
@@ -102,7 +146,7 @@ export default ObjectController.extend(ModalFunctionality, {
   **/
   reset: function() {
     this.setProperties({
-      email: null,
+      emailOrUsername: null,
       groupNames: null,
       error: false,
       saving: false,
@@ -126,13 +170,15 @@ export default ObjectController.extend(ModalFunctionality, {
       var userInvitedController = this.get('controllers.user-invited');
 
       this.setProperties({ saving: true, error: false });
-      this.get('model').createInvite(this.get('email'), groupNames).then(function() {
+      this.get('model').createInvite(this.get('emailOrUsername'), groupNames).then(function(result) {
         self.setProperties({ saving: false, finished: true });
         if (!self.get('invitingToTopic')) {
           Discourse.Invite.findInvitedBy(Discourse.User.current()).then(function (invite_model) {
             userInvitedController.set('model', invite_model);
             userInvitedController.set('totalInvites', invite_model.invites.length);
           });
+        } else if (self.get('isMessage') && result && result.user) {
+          self.get('model.details.allowed_users').pushObject(result.user);
         }
       }).catch(function() {
         self.setProperties({ saving: false, error: true });
diff --git a/app/assets/javascripts/discourse/routes/topic.js.es6 b/app/assets/javascripts/discourse/routes/topic.js.es6
index d7948ce3a35..725c895ead2 100644
--- a/app/assets/javascripts/discourse/routes/topic.js.es6
+++ b/app/assets/javascripts/discourse/routes/topic.js.es6
@@ -69,16 +69,6 @@ const TopicRoute = Discourse.Route.extend(ShowFooter, {
       this.controllerFor('invite').reset();
     },
 
-    showPrivateInvite() {
-      showModal('invitePrivate', this.modelFor('topic'));
-      this.controllerFor('invitePrivate').setProperties({
-        email: null,
-        error: false,
-        saving: false,
-        finished: false
-      });
-    },
-
     showHistory(post) {
       showModal('history', post);
       this.controllerFor('history').refresh(post.get("id"), "latest");
diff --git a/app/assets/javascripts/discourse/templates/modal/invite.hbs b/app/assets/javascripts/discourse/templates/modal/invite.hbs
index 3b74f7afab0..52a8767298b 100644
--- a/app/assets/javascripts/discourse/templates/modal/invite.hbs
+++ b/app/assets/javascripts/discourse/templates/modal/invite.hbs
@@ -2,7 +2,7 @@
   {{#if error}}
     <div class="alert alert-error">
       <button class="close" data-dismiss="alert">×</button>
-      {{i18n 'topic.invite_reply.error'}}
+      {{errorMessage}}
     </div>
   {{/if}}
 
@@ -11,9 +11,13 @@
   {{else}}
 
     <label>{{inviteInstructions}}</label>
-    {{text-field value=email placeholderKey="topic.invite_reply.email_placeholder"}}
+    {{#if allowExistingMembers}}
+      {{user-selector single="true" allowAny=true usernames=emailOrUsername includeGroups="true" placeholderKey="topic.invite_private.email_or_username_placeholder"}}
+    {{else}}
+      {{text-field value=emailOrUsername placeholderKey="topic.invite_reply.email_placeholder"}}
+    {{/if}}
 
-    {{#if isAdmin}}
+    {{#if showGroups}}
       <label>{{{groupInstructions}}}</label>
       {{group-selector groupFinder=groupFinder groupNames=groupNames placeholderKey="topic.invite_private.group_name"}}
     {{/if}}
diff --git a/app/assets/javascripts/discourse/templates/modal/invite_private.hbs b/app/assets/javascripts/discourse/templates/modal/invite_private.hbs
deleted file mode 100644
index 0284697cefd..00000000000
--- a/app/assets/javascripts/discourse/templates/modal/invite_private.hbs
+++ /dev/null
@@ -1,23 +0,0 @@
-<div class="modal-body">
-  {{#if error}}
-    <div class="alert alert-error">
-      <button class="close" data-dismiss="alert">×</button>
-      {{i18n 'topic.invite_private.error'}}
-    </div>
-  {{/if}}
-
-  {{#if finished}}
-    {{i18n 'topic.invite_private.success'}}
-  {{else}}
-    <label>{{i18n 'topic.invite_private.email_or_username'}}</label>
-    {{user-selector single="true" allowAny=true usernames=emailOrUsername includeGroups="true" placeholderKey="topic.invite_private.email_or_username_placeholder"}}
-  {{/if}}
-</div>
-<div class="modal-footer">
-  {{#if finished}}
-    <button class='btn btn-primary' {{action "closeModal"}}>{{i18n 'close'}}</button>
-  {{else}}
-    <button class='btn btn-primary' {{bind-attr disabled="disabled"}} {{action "invite"}}>{{buttonTitle}}</button>
-  {{/if}}
-
-</div>
diff --git a/app/assets/javascripts/discourse/views/invite-private.js.es6 b/app/assets/javascripts/discourse/views/invite-private.js.es6
deleted file mode 100644
index 461a6e102de..00000000000
--- a/app/assets/javascripts/discourse/views/invite-private.js.es6
+++ /dev/null
@@ -1,6 +0,0 @@
-import ModalBodyView from "discourse/views/modal-body";
-
-export default ModalBodyView.extend({
-  templateName: 'modal/invite_private',
-  title: I18n.t('topic.invite_private.title')
-});
diff --git a/app/assets/javascripts/discourse/views/invite.js.es6 b/app/assets/javascripts/discourse/views/invite.js.es6
index 03f4a72c4dc..0c4a5b67a65 100644
--- a/app/assets/javascripts/discourse/views/invite.js.es6
+++ b/app/assets/javascripts/discourse/views/invite.js.es6
@@ -4,9 +4,13 @@ export default ModalBodyView.extend({
   templateName: 'modal/invite',
 
   title: function() {
-    return this.get('controller.invitingToTopic') ?
-           I18n.t('topic.invite_reply.title') :
-           I18n.t('user.invited.create');
-  }.property('controller.invitingToTopic')
+    if (this.get('controller.isMessage')) {
+      return I18n.t('topic.invite_private.title');
+    } else if (this.get('controller.invitingToTopic')) {
+      return I18n.t('topic.invite_reply.title');
+    } else {
+      return I18n.t('user.invited.create');
+    }
+  }.property('controller.{invitingToTopic,isMessage}')
 
 });
diff --git a/app/assets/javascripts/discourse/views/topic-map-container.js.es6 b/app/assets/javascripts/discourse/views/topic-map-container.js.es6
index 5dee27706c3..b12cdd45e32 100644
--- a/app/assets/javascripts/discourse/views/topic-map-container.js.es6
+++ b/app/assets/javascripts/discourse/views/topic-map-container.js.es6
@@ -51,8 +51,7 @@ export default DiscourseContainerView.extend({
 
     // If we have a private message
     if (this.get('topic.isPrivateMessage')) {
-      container.attachViewWithArgs({ topic: topic, showPrivateInviteAction: 'showPrivateInvite' }, PrivateMessageMapComponent);
+      container.attachViewWithArgs({ topic: topic, showPrivateInviteAction: 'showInvite' }, PrivateMessageMapComponent);
     }
   }
 });
-
diff --git a/app/mailers/user_notifications.rb b/app/mailers/user_notifications.rb
index 5fede4157ef..a977ba653f5 100644
--- a/app/mailers/user_notifications.rb
+++ b/app/mailers/user_notifications.rb
@@ -124,6 +124,11 @@ class UserNotifications < ActionMailer::Base
     notification_email(user, opts)
   end
 
+  def user_invited_to_topic(user, opts)
+    opts[:show_category_in_subject] = true
+    notification_email(user, opts)
+  end
+
   def mailing_list_notify(user, post)
     send_notification_email(
       title: post.topic.title,
@@ -188,11 +193,12 @@ class UserNotifications < ActionMailer::Base
     use_site_subject = opts[:use_site_subject]
     add_re_to_subject = opts[:add_re_to_subject]
     show_category_in_subject = opts[:show_category_in_subject]
+    original_username = @notification.data_hash[:original_username] || @notification.data_hash[:display_username]
 
     send_notification_email(
       title: title,
       post: @post,
-      username: @notification.data_hash[:original_username],
+      username: original_username,
       from_alias: user_name,
       allow_reply_by_email: allow_reply_by_email,
       use_site_subject: use_site_subject,
diff --git a/app/models/notification.rb b/app/models/notification.rb
index bd96c36dc98..3c0565907fb 100644
--- a/app/models/notification.rb
+++ b/app/models/notification.rb
@@ -31,7 +31,7 @@ class Notification < ActiveRecord::Base
     @types ||= Enum.new(
       :mentioned, :replied, :quoted, :edited, :liked, :private_message,
       :invited_to_private_message, :invitee_accepted, :posted, :moved_post,
-      :linked, :granted_badge
+      :linked, :granted_badge, :invited_to_topic
     )
   end
 
diff --git a/app/models/topic.rb b/app/models/topic.rb
index eada4a11ff4..d48bf6ccc53 100644
--- a/app/models/topic.rb
+++ b/app/models/topic.rb
@@ -537,7 +537,7 @@ class Topic < ActiveRecord::Base
   # Invite a user to the topic by username or email. Returns success/failure
   def invite(invited_by, username_or_email, group_ids=nil)
     if private_message?
-      # If the user exists, add them to the topic.
+      # If the user exists, add them to the message.
       user = User.find_by_username_or_email(username_or_email)
       if user && topic_allowed_users.create!(user_id: user.id)
 
@@ -555,7 +555,20 @@ class Topic < ActiveRecord::Base
       # NOTE callers expect an invite object if an invite was sent via email
       invite_by_email(invited_by, username_or_email, group_ids)
     else
-      false
+      # invite existing member to a topic
+      user = User.find_by_username_or_email(username_or_email)
+      if user && topic_allowed_users.create!(user_id: user.id)
+
+        # Notify the user they've been invited
+        user.notifications.create(notification_type: Notification.types[:invited_to_topic],
+                                  topic_id: id,
+                                  post_number: 1,
+                                  data: { topic_title: title,
+                                          display_username: invited_by.username }.to_json)
+        return true
+      else
+        false
+      end
     end
   end
 
diff --git a/app/models/user_email_observer.rb b/app/models/user_email_observer.rb
index 034a2e6492a..e2389f5bb4f 100644
--- a/app/models/user_email_observer.rb
+++ b/app/models/user_email_observer.rb
@@ -32,6 +32,10 @@ class UserEmailObserver < ActiveRecord::Observer
       enqueue :user_invited_to_private_message
     end
 
+    def invited_to_topic
+      enqueue :user_invited_to_topic
+    end
+
     private
 
     def enqueue(type)
diff --git a/config/locales/client.en.yml b/config/locales/client.en.yml
index e93fc713b6a..7521f986c76 100644
--- a/config/locales/client.en.yml
+++ b/config/locales/client.en.yml
@@ -484,7 +484,7 @@ en:
         weekly: "weekly"
         every_two_weeks: "every two weeks"
 
-      email_direct: "Send me an email when someone quotes me, replies to my post, or mentions my @username"
+      email_direct: "Send me an email when someone quotes me, replies to my post, or mentions my @username or invites me to a topic"
       email_private_messages: "Send me an email when someone messages me"
       email_always: "Do not suppress email notifications when I am active on the site"
 
@@ -789,6 +789,7 @@ en:
       liked: "<i title='liked' class='fa fa-heart'></i><p><span>{{username}}</span> {{description}}</p>"
       private_message: "<i title='private message' class='fa fa-envelope-o'></i><p><span>{{username}}</span> {{description}}</p>"
       invited_to_private_message: "<i title='private message' class='fa fa-envelope-o'></i><p><span>{{username}}</span> {{description}}</p>"
+      invited_to_topic: "<i title='invited to topic' class='fa fa-envelope-o'></i><p><span>{{username}}</span> {{description}}</p>"
       invitee_accepted: "<i title='accepted your invitation' class='fa fa-user'></i><p><span>{{username}}</span> accepted your invitation</p>"
       moved_post: "<i title='moved post' class='fa fa-sign-out'></i><p><span>{{username}}</span> moved {{description}}</p>"
       linked: "<i title='linked post' class='fa fa-arrow-left'></i><p><span>{{username}}</span> {{description}}</p>"
@@ -1072,14 +1073,14 @@ en:
 
       invite_reply:
         title: 'Invite'
-        action: 'Email Invite'
+        action: 'Send Invite'
         help: 'send invitations to friends so they can reply to this topic with a single click'
         to_topic: "We'll send a brief email allowing your friend to immediately join and reply to this topic by clicking a link, no login required."
         to_forum: "We'll send a brief email allowing your friend to immediately join by clicking a link, no login required."
 
         email_placeholder: 'name@example.com'
-        success: "We mailed out an invitation to <b>{{email}}</b>. We'll notify you when the invitation is redeemed. Check the invitations tab on your user page to keep track of your invites."
-        error: "Sorry, we couldn't invite that person. Perhaps they are already a user? (Invites are rate limited)"
+        success: "We mailed out an invitation to <b>{{emailOrUsername}}</b>. We'll notify you when the invitation is redeemed. Check the invitations tab on your user page to keep track of your invites."
+        error: "Sorry, we couldn't invite that person. Perhaps they have already been invited? (Invites are rate limited)"
 
       login_reply: 'Log In to Reply'
 
diff --git a/config/locales/server.en.yml b/config/locales/server.en.yml
index 45b611185bf..c366ac77d8f 100644
--- a/config/locales/server.en.yml
+++ b/config/locales/server.en.yml
@@ -1158,6 +1158,7 @@ en:
     moved_post: "%{display_username} moved your post to %{link}"
     private_message: "%{display_username} sent you a message: %{link}"
     invited_to_private_message: "%{display_username} invited you to a message: %{link}"
+    invited_to_topic: "%{display_username} invited you to a topic: %{link}"
     invitee_accepted: "%{display_username} accepted your invitation"
     linked: "%{display_username} linked you in %{link}"
     granted_badge: "You earned %{link}"
@@ -1773,6 +1774,13 @@ en:
 
         Please visit this link to view the topic: %{base_url}%{url}
 
+    user_invited_to_topic:
+      subject_template: "[%{site_name}] %{username} invited you to a topic '%{topic_title}'"
+      text_body_template: |
+        %{username} invited you to a topic '%{topic_title}' on %{site_name}:
+
+        Please visit this link to view the topic: %{base_url}%{url}
+
     user_replied:
       subject_template: "[%{site_name}] %{topic_title}"
       text_body_template: |
diff --git a/spec/mailers/user_notifications_spec.rb b/spec/mailers/user_notifications_spec.rb
index 18921cfb97b..100b5cfb172 100644
--- a/spec/mailers/user_notifications_spec.rb
+++ b/spec/mailers/user_notifications_spec.rb
@@ -326,4 +326,11 @@ describe UserNotifications do
     end
   end
 
+  describe "user invited to a topic" do
+    include_examples "notification email building" do
+      let(:notification_type) { :invited_to_topic }
+      include_examples "no reply by email"
+    end
+  end
+
 end
diff --git a/spec/models/user_email_observer_spec.rb b/spec/models/user_email_observer_spec.rb
index 331d6eb636c..20c632e1293 100644
--- a/spec/models/user_email_observer_spec.rb
+++ b/spec/models/user_email_observer_spec.rb
@@ -98,4 +98,22 @@ describe UserEmailObserver do
 
   end
 
+  context 'user_invited_to_topic' do
+
+    let(:user) { Fabricate(:user) }
+    let!(:notification) { Fabricate(:notification, user: user, notification_type: 13) }
+
+    it "enqueues a job for the email" do
+      Jobs.expects(:enqueue_in).with(SiteSetting.email_time_window_mins.minutes, :user_email, type: :user_invited_to_topic, user_id: notification.user_id, notification_id: notification.id)
+      UserEmailObserver.send(:new).after_commit(notification)
+    end
+
+    it "doesn't enqueue an email if the user has mention emails disabled" do
+      user.expects(:email_direct?).returns(false)
+      Jobs.expects(:enqueue_in).with(SiteSetting.email_time_window_mins.minutes, :user_email, has_entry(type: :user_invited_to_topic)).never
+      UserEmailObserver.send(:new).after_commit(notification)
+    end
+
+  end
+
 end