diff --git a/core/includes/form.inc b/core/includes/form.inc
index c94bc62..ea4b5df 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -3832,20 +3832,8 @@ function form_process_autocomplete($element, &$form_state) {
   if (!empty($element['#autocomplete_path']) && drupal_valid_path($element['#autocomplete_path'])) {
     $element['#attributes']['class'][] = 'form-autocomplete';
     $element['#attached']['library'][] = array('system', 'drupal.autocomplete');
-    // Provide a hidden element for the JavaScript behavior to bind to. Since
-    // this element is for client-side functionality only, and we don't want to
-    // collect any input from it, use #theme='hidden' instead of #type='hidden'.
-    // @todo Refactor autocomplete.js to accept Drupal.settings instead of
-    //   requiring extraneous markup.
-    $element['autocomplete'] = array(
-      '#theme' => 'hidden',
-      '#attributes' => array(
-        'id' => $element['#id'] . '-autocomplete',
-        'value' => url($element['#autocomplete_path'], array('absolute' => TRUE)),
-        'class' => array('autocomplete'),
-        'disabled' => 'disabled',
-      ),
-    );
+    // Provide a data attribute for the JavaScript behavior to bind to.
+    $element['#attributes']['data-autocomplete-path'] = url($element['#autocomplete_path'], array('absolute' => TRUE));
   }
   return $element;
 }
diff --git a/core/misc/autocomplete.js b/core/misc/autocomplete.js
index 0ffe404..489dd73 100644
--- a/core/misc/autocomplete.js
+++ b/core/misc/autocomplete.js
@@ -1,334 +1,140 @@
-(function ($) {
+(function ($, Drupal) {
 
 "use strict";
 
 /**
- * Attaches the autocomplete behavior to all required fields.
- */
-Drupal.behaviors.autocomplete = {
-  attach: function (context, settings) {
-    var acdb = [];
-    $(context).find('input.autocomplete').once('autocomplete', function () {
-      var uri = this.value;
-      if (!acdb[uri]) {
-        acdb[uri] = new Drupal.ACDB(uri);
+ * Splits multi-values input text.
+ *
+ * @param {String} value
+ *
+ * @return {Array}
+ */
+function split(value) {
+  return value.split(/,\s*/);
+}
+
+/**
+ * Returns the last value of an multi-value textfield.
+ *
+ * @param {String} terms
+ *
+ * @return {String}
+ */
+function extractLast(terms) {
+  return autocomplete.split(terms).pop();
+}
+
+/**
+ * jQuery UI autocomplete source callback.
+ *
+ * @param {Object} request
+ * @param {Function} response
+ */
+function source(request, response) {
+  // Get the desired term and construct the autocomplete URL for it.
+  var term = autocomplete.extractLast(request.term);
+  var url = this.element.data('autocompletePath') + '/' + encodeURIComponent(term);
+
+  /**
+   * Transforms the data object into an array and update autocomplete results.
+   *
+   * @param {Object} data
+   */
+  function sourceCallback(data) {
+    // Drupal returns an object, we need an array.
+    var terms = [];
+    for (var i in data) {
+      if (data.hasOwnProperty(i)) {
+        terms.push(data[i]);
       }
-      var $input = $('#' + this.id.substr(0, this.id.length - 13))
-        .attr('autocomplete', 'OFF')
-        .attr('aria-autocomplete', 'list');
-      $($input[0].form).submit(Drupal.autocompleteSubmit);
-      $input.parent()
-        .attr('role', 'application')
-        .append($('<span class="element-invisible" aria-live="assertive"></span>')
-          .attr('id', $input[0].id + '-autocomplete-aria-live')
-        );
-      new Drupal.jsAC($input, acdb[uri]);
-    });
-  }
-};
-
-/**
- * Prevents the form from submitting if the suggestions popup is open
- * and closes the suggestions popup when doing so.
- */
-Drupal.autocompleteSubmit = function () {
-  var $autocomplete = $('#autocomplete');
-  if ($autocomplete.length !== 0) {
-    $autocomplete[0].owner.hidePopup();
-  }
-  return $autocomplete.length === 0;
-};
-
-/**
- * An AutoComplete object.
- */
-Drupal.jsAC = function ($input, db) {
-  var ac = this;
-  this.input = $input[0];
-  this.ariaLive = $('#' + this.input.id + '-autocomplete-aria-live');
-  this.db = db;
-
-  $input
-    .keydown(function (event) { return ac.onkeydown(this, event); })
-    .keyup(function (event) { ac.onkeyup(this, event); })
-    .blur(function () { ac.hidePopup(); ac.db.cancel(); });
-};
-
-/**
- * Handler for the "keydown" event.
- */
-Drupal.jsAC.prototype.onkeydown = function (input, e) {
-  if (!e) {
-    e = window.event;
-  }
-  switch (e.keyCode) {
-    case 40: // down arrow.
-      this.selectDown();
-      return false;
-    case 38: // up arrow.
-      this.selectUp();
-      return false;
-    default: // All other keys.
-      return true;
-  }
-};
-
-/**
- * Handler for the "keyup" event.
- */
-Drupal.jsAC.prototype.onkeyup = function (input, e) {
-  if (!e) {
-    e = window.event;
-  }
-  switch (e.keyCode) {
-    case 16: // Shift.
-    case 17: // Ctrl.
-    case 18: // Alt.
-    case 20: // Caps lock.
-    case 33: // Page up.
-    case 34: // Page down.
-    case 35: // End.
-    case 36: // Home.
-    case 37: // Left arrow.
-    case 38: // Up arrow.
-    case 39: // Right arrow.
-    case 40: // Down arrow.
-      return true;
-
-    case 9:  // Tab.
-    case 13: // Enter.
-    case 27: // Esc.
-      this.hidePopup(e.keyCode);
-      return true;
-
-    default: // All other keys.
-      if (input.value.length > 0 && !input.readOnly) {
-        this.populatePopup();
-      }
-      else {
-        this.hidePopup(e.keyCode);
-      }
-      return true;
-  }
-};
-
-/**
- * Puts the currently highlighted suggestion into the autocomplete field.
- */
-Drupal.jsAC.prototype.select = function (node) {
-  this.input.value = $(node).data('autocompleteValue');
-};
-
-/**
- * Highlights the next suggestion.
- */
-Drupal.jsAC.prototype.selectDown = function () {
-  if (this.selected && this.selected.nextSibling) {
-    this.highlight(this.selected.nextSibling);
-  }
-  else if (this.popup) {
-    var lis = $(this.popup).find('li');
-    if (lis.length > 0) {
-      this.highlight(lis.get(0));
     }
+    // Send the new string array of terms to the jQuery UI list.
+    response(terms);
   }
-};
+  // Make the AJAX request.
+  $.getJSON(url, sourceCallback);
+}
 
 /**
- * Highlights the previous suggestion.
+ * Handles an autocompletesearch event.
+ *
+ * @return {Boolean}
  */
-Drupal.jsAC.prototype.selectUp = function () {
-  if (this.selected && this.selected.previousSibling) {
-    this.highlight(this.selected.previousSibling);
+function searchHandler() {
+  // Only search if there has been more then two characters in there.
+  var term = autocomplete.extractLast(this.value);
+  if (term.length < 1) {
+    return false;
   }
-};
+}
 
 /**
- * Highlights a suggestion.
+ * Handles an autocompletefocus event.
+ *
+ * @return {Boolean}
  */
-Drupal.jsAC.prototype.highlight = function (node) {
-  // Unhighlights a suggestion for "keyup" and "keydown" events.
-  if (this.selected !== false) {
-    $(this.selected).removeClass('selected');
-  }
-  $(node).addClass('selected');
-  this.selected = node;
-  $(this.ariaLive).html($(this.selected).html());
-};
+function focusHandler() {
+  return false;
+}
 
 /**
- * Unhighlights a suggestion.
+ * Handles an autocompleteselect event.
+ *
+ * @param {Object} event
+ * @param {Object} ui
+ *
+ * @return {Boolean}
  */
-Drupal.jsAC.prototype.unhighlight = function (node) {
-  $(node).removeClass('selected');
-  this.selected = false;
-  $(this.ariaLive).empty();
-};
+function selectHandler(event, ui) {
+  var terms = autocomplete.split(this.value);
+  // Remove the current input.
+  terms.pop();
+  // Add the selected item.
+  terms.push(ui.item.value);
+  this.value = terms.join(", ");
+  return false;
+}
 
-/**
- * Hides the autocomplete suggestions.
- */
-Drupal.jsAC.prototype.hidePopup = function (keycode) {
-  // Select item if the right key or mousebutton was pressed.
-  if (this.selected && ((keycode && keycode !== 46 && keycode !== 8 && keycode !== 27) || !keycode)) {
-    this.input.value = $(this.selected).data('autocompleteValue');
-  }
-  // Hide popup.
-  var popup = this.popup;
-  if (popup) {
-    this.popup = null;
-    $(popup).fadeOut('fast', function () { $(popup).remove(); });
-  }
-  this.selected = false;
-  $(this.ariaLive).empty();
-};
 
-/**
- * Positions the suggestions popup and starts a search.
- */
-Drupal.jsAC.prototype.populatePopup = function () {
-  var $input = $(this.input);
-  var position = $input.position();
-  // Show popup.
-  if (this.popup) {
-    $(this.popup).remove();
+var autocomplete = {
+  split: split,
+  extractLast: extractLast,
+  options: {
+    // The autcomplete source is provided by the data-autocomplete-path
+    // attribute within the element itself.
+    source: source,
+    search: searchHandler,
+    focus: focusHandler,
+    // It will select the search term based on the last item in the list.
+    select: selectHandler
   }
-  this.selected = false;
-  this.popup = $('<div id="autocomplete"></div>')[0];
-  this.popup.owner = this;
-  $(this.popup).css({
-    top: parseInt(position.top + this.input.offsetHeight, 10) + 'px',
-    left: parseInt(position.left, 10) + 'px',
-    width: $input.innerWidth() + 'px',
-    display: 'none'
-  });
-  $input.before(this.popup);
-
-  // Do search.
-  this.db.owner = this;
-  this.db.search(this.input.value);
 };
 
 /**
- * Fills the suggestion popup with any matches received.
+ * Attaches the autocomplete behavior to all required fields.
  */
-Drupal.jsAC.prototype.found = function (matches) {
-  // If no value in the textfield, do not show the popup.
-  if (!this.input.value.length) {
-    return false;
-  }
-
-  // Prepare matches.
-  var ul = $('<ul></ul>');
-  var ac = this;
-  for (var key in matches) {
-    if (matches.hasOwnProperty(key)) {
-      $('<li></li>')
-        .html($('<div></div>').html(matches[key]))
-        .mousedown(function () { ac.select(this); })
-        .mouseover(function () { ac.highlight(this); })
-        .mouseout(function () { ac.unhighlight(this); })
-        .data('autocompleteValue', key)
-        .appendTo(ul);
-    }
-  }
-
-  // Show popup with matches, if any.
-  if (this.popup) {
-    if (ul.children().length) {
-      $(this.popup).empty().append(ul).show();
-      $(this.ariaLive).html(Drupal.t('Autocomplete popup'));
-    }
-    else {
-      $(this.popup).css({ visibility: 'hidden' });
-      this.hidePopup();
+Drupal.behaviors.autocomplete = {
+  attach: function (context, settings) {
+    // Act on textfields with the "form-autocomplete" class.
+    var $autocomplete = $(context).find('input.form-autocomplete').once('autocomplete');
+    $autocomplete.each(function () {
+      // Use jQuery UI Autocomplete on the textfield.
+      $(this).autocomplete(autocomplete.options);
+    });
+  },
+  detach: function (context, settings, trigger) {
+    if (trigger === 'unload') {
+      var $autocomplete = $(context).find('input.form-autocomplete').removeOnce('autocomplete');
+      $autocomplete.each(function () {
+        $(this).autocomplete('destroy');
+      });
     }
   }
 };
 
-Drupal.jsAC.prototype.setStatus = function (status) {
-  switch (status) {
-    case 'begin':
-      $(this.input).addClass('throbbing');
-      $(this.ariaLive).html(Drupal.t('Searching for matches...'));
-      break;
-    case 'cancel':
-    case 'error':
-    case 'found':
-      $(this.input).removeClass('throbbing');
-      break;
-  }
-};
-
-/**
- * An AutoComplete DataBase object.
- */
-Drupal.ACDB = function (uri) {
-  this.uri = uri;
-  this.delay = 300;
-  this.cache = {};
-};
-
-/**
- * Performs a cached and delayed search.
- */
-Drupal.ACDB.prototype.search = function (searchString) {
-  var db = this;
-  this.searchString = searchString;
-
-  // See if this string needs to be searched for anyway.
-  searchString = searchString.replace(/^\s+|\s+$/, '');
-  if (searchString.length <= 0 ||
-    searchString.charAt(searchString.length - 1) === ',') {
-    return;
-  }
-
-  // See if this key has been searched for before.
-  if (this.cache[searchString]) {
-    return this.owner.found(this.cache[searchString]);
-  }
-
-  // Initiate delayed search.
-  if (this.timer) {
-    clearTimeout(this.timer);
-  }
-  this.timer = setTimeout(function () {
-    db.owner.setStatus('begin');
-
-    // Ajax GET request for autocompletion. We use Drupal.encodePath instead of
-    // encodeURIComponent to allow autocomplete search terms to contain slashes.
-    $.ajax({
-      type: 'GET',
-      url: db.uri + '/' + Drupal.encodePath(searchString),
-      dataType: 'json',
-      success: function (matches) {
-        if (typeof matches.status === 'undefined' || matches.status !== 0) {
-          db.cache[searchString] = matches;
-          // Verify if these are still the matches the user wants to see.
-          if (db.searchString === searchString) {
-            db.owner.found(matches);
-          }
-          db.owner.setStatus('found');
-        }
-      },
-      error: function (xmlhttp) {
-        alert(Drupal.ajaxError(xmlhttp, db.uri));
-      }
-    });
-  }, this.delay);
-};
-
 /**
- * Cancels the current autocomplete request.
+ * Expose autocomplete settings.
  */
-Drupal.ACDB.prototype.cancel = function () {
-  if (this.owner) {
-    this.owner.setStatus('cancel');
-  }
-  if (this.timer) {
-    clearTimeout(this.timer);
-  }
-  this.searchString = '';
-};
+Drupal.autocomplete = Drupal.autocomplete || autocomplete;
 
-})(jQuery);
+})(jQuery, Drupal);
diff --git a/core/modules/system/system.base-rtl.css b/core/modules/system/system.base-rtl.css
index d01792e..73b80fb 100644
--- a/core/modules/system/system.base-rtl.css
+++ b/core/modules/system/system.base-rtl.css
@@ -1,4 +1,3 @@
-
 /**
  * @file
  * Generic theme-independent base styles.
@@ -11,7 +10,7 @@
 .js input.form-autocomplete {
   background-position: 0% 2px;
 }
-.js input.throbbing {
+.js input.form-autocomplete.ui-autocomplete-loading {
   background-position: 0% -18px;
 }
 
diff --git a/core/modules/system/system.base.css b/core/modules/system/system.base.css
index 68a1683..26215e2 100644
--- a/core/modules/system/system.base.css
+++ b/core/modules/system/system.base.css
@@ -1,40 +1,15 @@
-
 /**
  * @file
  * Generic theme-independent base styles.
  */
 
-/**
- * Autocomplete.
- *
- * @see autocomplete.js
- */
-/* Suggestion list */
-#autocomplete {
-  border: 1px solid;
-  overflow: hidden;
-  position: absolute;
-  z-index: 100;
-}
-#autocomplete ul {
-  list-style: none;
-  list-style-image: none;
-  margin: 0;
-  padding: 0;
-}
-#autocomplete li {
-  background: #fff;
-  color: #000;
-  cursor: default;
-  white-space: pre;
-}
 /* Animated throbber */
 .js input.form-autocomplete {
   background-image: url(../../misc/throbber.gif);
   background-position: 100% 2px; /* LTR */
   background-repeat: no-repeat;
 }
-.js input.throbbing {
+.js input.form-autocomplete.ui-autocomplete-loading {
   background-position: 100% -18px; /* LTR */
 }
 
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index d43455e..8f4f4e3 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -1285,6 +1285,9 @@ function system_library_info() {
     'js' => array(
       'core/misc/autocomplete.js' => array('group' => JS_DEFAULT),
     ),
+    'dependencies' => array(
+      array('system', 'jquery.ui.autocomplete'),
+    ),
   );
 
   // jQuery.
@@ -1526,7 +1529,7 @@ function system_library_info() {
     'website' => 'http://jqueryui.com/demos/position/',
     'version' => $libraries['jquery.ui.core']['version'],
     'js' => array(
-      'core/misc/ui/jquery.ui.position.min.js' => array(),
+      'core/misc/ui/ui/jquery.ui.position.js' => array(),
     ),
   );
   $libraries['jquery.ui.progressbar'] = array(
@@ -1657,7 +1660,7 @@ function system_library_info() {
       'core/misc/ui/ui/jquery.ui.widget.js' => array('group' => JS_LIBRARY, 'weight' => -10),
     ),
     'dependencies' => array(
-      array('system', 'ui'),
+      array('system', 'jquery.ui.core'),
     ),
   );
   $libraries['jquery.effects.core'] = array(
diff --git a/core/themes/bartik/css/style-rtl.css b/core/themes/bartik/css/style-rtl.css
index 90638eb..111c764 100644
--- a/core/themes/bartik/css/style-rtl.css
+++ b/core/themes/bartik/css/style-rtl.css
@@ -225,7 +225,7 @@ ul.action-links li a {
 .js input.form-autocomplete {
   background-position: 1% 4px;
 }
-.js input.throbbing {
+.js input.form-autocomplete.ui-autocomplete-loading {
   background-position: 1% -16px;
 }
 
diff --git a/core/themes/bartik/css/style.css b/core/themes/bartik/css/style.css
index 0531e49..9ae4408 100644
--- a/core/themes/bartik/css/style.css
+++ b/core/themes/bartik/css/style.css
@@ -1,4 +1,3 @@
-
 /* ---------- Overall Specifications ---------- */
 
 body {
@@ -1275,7 +1274,7 @@ input.form-button-disabled:active,
 .js input.form-autocomplete {
   background-position: 100% 4px; /* LTR */
 }
-.js input.throbbing {
+.js input.form-autocomplete.ui-autocomplete-loading {
   background-position: 100% -16px; /* LTR */
 }
 
diff --git a/core/themes/seven/style.css b/core/themes/seven/style.css
index 380aec8..9d5fbef 100644
--- a/core/themes/seven/style.css
+++ b/core/themes/seven/style.css
@@ -1,4 +1,3 @@
-
 /**
  * Generic elements.
  */
@@ -603,7 +602,6 @@ div.teaser-checkbox .form-item,
 .form-item label.option input {
   vertical-align: middle;
 }
-.form-disabled input.form-autocomplete,
 .form-disabled input.form-text,
 .form-disabled input.form-tel,
 .form-disabled input.form-email,
@@ -694,7 +692,6 @@ input.form-button-disabled:active {
   text-shadow: none;
   color: #999;
 }
-input.form-autocomplete,
 input.form-text,
 input.form-tel,
 input.form-email,
@@ -729,12 +726,6 @@ select.form-select:focus {
   box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.1), 0 0 8px rgba(220, 220, 220, 0.4);
   outline-color: rgba(0, 116, 189, 0.5);
 }
-.js input.form-autocomplete {
-  background-position: 100% 4px;
-}
-.js input.throbbing {
-  background-position: 100% -16px;
-}
 ul.action-links {
   margin: 1em 0;
   padding: 0 20px 0 20px; /* LTR */