diff --git a/django/forms/widgets.py b/django/forms/widgets.py
index 8ccf939acd..6ccbb86274 100644
--- a/django/forms/widgets.py
+++ b/django/forms/widgets.py
@@ -670,7 +670,7 @@ class Select(ChoiceWidget):
     def get_context(self, name, value, attrs):
         context = super().get_context(name, value, attrs)
         if self.allow_multiple_selected:
-            context['widget']['attrs']['multiple'] = 'multiple'
+            context['widget']['attrs']['multiple'] = True
         return context
 
     @staticmethod
diff --git a/docs/ref/forms/widgets.txt b/docs/ref/forms/widgets.txt
index 12677eb908..dc6256ee06 100644
--- a/docs/ref/forms/widgets.txt
+++ b/docs/ref/forms/widgets.txt
@@ -664,7 +664,7 @@ that specifies the template used to render each choice. For example, for the
     * ``option_template_name``: ``'django/forms/widgets/select_option.html'``
 
     Similar to :class:`Select`, but allows multiple selection:
-    ``<select multiple="multiple">...</select>``
+    ``<select multiple>...</select>``
 
 ``RadioSelect``
 ~~~~~~~~~~~~~~~
diff --git a/docs/releases/2.1.txt b/docs/releases/2.1.txt
index b979ba2224..2c1f199577 100644
--- a/docs/releases/2.1.txt
+++ b/docs/releases/2.1.txt
@@ -251,6 +251,10 @@ Miscellaneous
 * ``allowed_hosts`` is now a required argument of private API
   ``django.utils.http.is_safe_url()``.
 
+* The ``multiple`` attribute rendered by the
+  :class:`~django.forms.SelectMultiple` widget now uses HTML5 boolean syntax
+  rather than XHTML's ``mulitple="multiple"``.
+
 .. _deprecated-features-2.1:
 
 Features deprecated in 2.1
diff --git a/tests/admin_widgets/tests.py b/tests/admin_widgets/tests.py
index 0ce1c8e5d9..8c3f06670c 100644
--- a/tests/admin_widgets/tests.py
+++ b/tests/admin_widgets/tests.py
@@ -255,7 +255,7 @@ class FilteredSelectMultipleWidgetTest(SimpleTestCase):
         w = widgets.FilteredSelectMultiple('test\\', False)
         self.assertHTMLEqual(
             w.render('test', 'test'),
-            '<select multiple="multiple" name="test" class="selectfilter" '
+            '<select multiple name="test" class="selectfilter" '
             'data-field-name="test\\" data-is-stacked="0">\n</select>'
         )
 
@@ -264,7 +264,7 @@ class FilteredSelectMultipleWidgetTest(SimpleTestCase):
         w = widgets.FilteredSelectMultiple('test\\', True)
         self.assertHTMLEqual(
             w.render('test', 'test'),
-            '<select multiple="multiple" name="test" class="selectfilterstacked" '
+            '<select multiple name="test" class="selectfilterstacked" '
             'data-field-name="test\\" data-is-stacked="1">\n</select>'
         )
 
diff --git a/tests/forms_tests/field_tests/test_multivaluefield.py b/tests/forms_tests/field_tests/test_multivaluefield.py
index cd446d07ce..edb32957e3 100644
--- a/tests/forms_tests/field_tests/test_multivaluefield.py
+++ b/tests/forms_tests/field_tests/test_multivaluefield.py
@@ -129,7 +129,7 @@ class MultiValueFieldTest(SimpleTestCase):
             """
             <tr><th><label for="id_field1_0">Field1:</label></th>
             <td><input type="text" name="field1_0" id="id_field1_0" required />
-            <select multiple="multiple" name="field1_1" id="id_field1_1" required>
+            <select multiple name="field1_1" id="id_field1_1" required>
             <option value="J">John</option>
             <option value="P">Paul</option>
             <option value="G">George</option>
@@ -152,7 +152,7 @@ class MultiValueFieldTest(SimpleTestCase):
             """
             <tr><th><label for="id_field1_0">Field1:</label></th>
             <td><input type="text" name="field1_0" value="some text" id="id_field1_0" required />
-            <select multiple="multiple" name="field1_1" id="id_field1_1" required>
+            <select multiple name="field1_1" id="id_field1_1" required>
             <option value="J" selected>John</option>
             <option value="P" selected>Paul</option>
             <option value="G">George</option>
diff --git a/tests/forms_tests/tests/test_forms.py b/tests/forms_tests/tests/test_forms.py
index a6b157f044..4ec21f869e 100644
--- a/tests/forms_tests/tests/test_forms.py
+++ b/tests/forms_tests/tests/test_forms.py
@@ -760,7 +760,7 @@ Java</label></li>
             composers = MultipleChoiceField()
 
         f = SongForm(auto_id=False)
-        self.assertHTMLEqual(str(f['composers']), """<select multiple="multiple" name="composers" required>
+        self.assertHTMLEqual(str(f['composers']), """<select multiple name="composers" required>
 </select>""")
 
         class SongForm(Form):
@@ -768,13 +768,13 @@ Java</label></li>
             composers = MultipleChoiceField(choices=[('J', 'John Lennon'), ('P', 'Paul McCartney')])
 
         f = SongForm(auto_id=False)
-        self.assertHTMLEqual(str(f['composers']), """<select multiple="multiple" name="composers" required>
+        self.assertHTMLEqual(str(f['composers']), """<select multiple name="composers" required>
 <option value="J">John Lennon</option>
 <option value="P">Paul McCartney</option>
 </select>""")
         f = SongForm({'name': 'Yesterday', 'composers': ['P']}, auto_id=False)
         self.assertHTMLEqual(str(f['name']), '<input type="text" name="name" value="Yesterday" required />')
-        self.assertHTMLEqual(str(f['composers']), """<select multiple="multiple" name="composers" required>
+        self.assertHTMLEqual(str(f['composers']), """<select multiple name="composers" required>
 <option value="J">John Lennon</option>
 <option value="P" selected>Paul McCartney</option>
 </select>""")
@@ -1865,7 +1865,7 @@ Password: <input type="password" name="password" required /></li>"""
             p.as_ul(),
             """<li>Username: <input type="text" name="username" value="django" maxlength="10" required /></li>
 <li>Password: <input type="password" name="password" required /></li>
-<li>Options: <select multiple="multiple" name="options" required>
+<li>Options: <select multiple name="options" required>
 <option value="f" selected>foo</option>
 <option value="b" selected>bar</option>
 <option value="w">whiz</option>
@@ -1881,7 +1881,7 @@ Username: <input type="text" name="username" maxlength="10" required /></li>
 <li><ul class="errorlist"><li>This field is required.</li></ul>
 Password: <input type="password" name="password" required /></li>
 <li><ul class="errorlist"><li>This field is required.</li></ul>
-Options: <select multiple="multiple" name="options" required>
+Options: <select multiple name="options" required>
 <option value="f">foo</option>
 <option value="b">bar</option>
 <option value="w">whiz</option>
@@ -1895,7 +1895,7 @@ Options: <select multiple="multiple" name="options" required>
 <li><ul class="errorlist"><li>This field is required.</li></ul>
 Password: <input type="password" name="password" required /></li>
 <li><ul class="errorlist"><li>This field is required.</li></ul>
-Options: <select multiple="multiple" name="options" required>
+Options: <select multiple name="options" required>
 <option value="f">foo</option>
 <option value="b">bar</option>
 <option value="w">whiz</option>
@@ -1909,7 +1909,7 @@ Options: <select multiple="multiple" name="options" required>
             """<li>Username: <input type="text" name="username" value="foo" maxlength="10" required /></li>
 <li><ul class="errorlist"><li>This field is required.</li></ul>
 Password: <input type="password" name="password" required /></li>
-<li>Options: <select multiple="multiple" name="options" required>
+<li>Options: <select multiple name="options" required>
 <option value="f" selected>foo</option>
 <option value="b" selected>bar</option>
 <option value="w">whiz</option>
@@ -1938,7 +1938,7 @@ Password: <input type="password" name="password" required /></li>
             p.as_ul(),
             """<li>Username: <input type="text" name="username" value="django" maxlength="10" required /></li>
 <li>Password: <input type="password" name="password" required /></li>
-<li>Options: <select multiple="multiple" name="options" required>
+<li>Options: <select multiple name="options" required>
 <option value="f">foo</option>
 <option value="b" selected>bar</option>
 <option value="w" selected>whiz</option>
@@ -1949,7 +1949,7 @@ Password: <input type="password" name="password" required /></li>
             p.as_ul(),
             """<li>Username: <input type="text" name="username" value="stephane" maxlength="10" required /></li>
 <li>Password: <input type="password" name="password" required /></li>
-<li>Options: <select multiple="multiple" name="options" required>
+<li>Options: <select multiple name="options" required>
 <option value="f" selected>foo</option>
 <option value="b" selected>bar</option>
 <option value="w">whiz</option>
diff --git a/tests/forms_tests/tests/tests.py b/tests/forms_tests/tests/tests.py
index a54ad09c26..bf0d588f53 100644
--- a/tests/forms_tests/tests/tests.py
+++ b/tests/forms_tests/tests/tests.py
@@ -116,13 +116,13 @@ class ModelFormCallableModelDefault(TestCase):
 <option value="3">ChoiceOption 3</option>
 </select><input type="hidden" name="initial-choice_int" value="1" id="initial-id_choice_int" /></p>
 <p><label for="id_multi_choice">Multi choice:</label>
-<select multiple="multiple" name="multi_choice" id="id_multi_choice" required>
+<select multiple name="multi_choice" id="id_multi_choice" required>
 <option value="1" selected>ChoiceOption 1</option>
 <option value="2">ChoiceOption 2</option>
 <option value="3">ChoiceOption 3</option>
 </select><input type="hidden" name="initial-multi_choice" value="1" id="initial-id_multi_choice_0" /></p>
 <p><label for="id_multi_choice_int">Multi choice int:</label>
-<select multiple="multiple" name="multi_choice_int" id="id_multi_choice_int" required>
+<select multiple name="multi_choice_int" id="id_multi_choice_int" required>
 <option value="1" selected>ChoiceOption 1</option>
 <option value="2">ChoiceOption 2</option>
 <option value="3">ChoiceOption 3</option>
@@ -152,14 +152,14 @@ class ModelFormCallableModelDefault(TestCase):
 <option value="3">ChoiceOption 3</option>
 </select><input type="hidden" name="initial-choice_int" value="2" id="initial-id_choice_int" /></p>
 <p><label for="id_multi_choice">Multi choice:</label>
-<select multiple="multiple" name="multi_choice" id="id_multi_choice" required>
+<select multiple name="multi_choice" id="id_multi_choice" required>
 <option value="1">ChoiceOption 1</option>
 <option value="2" selected>ChoiceOption 2</option>
 <option value="3" selected>ChoiceOption 3</option>
 </select><input type="hidden" name="initial-multi_choice" value="2" id="initial-id_multi_choice_0" />
 <input type="hidden" name="initial-multi_choice" value="3" id="initial-id_multi_choice_1" /></p>
 <p><label for="id_multi_choice_int">Multi choice int:</label>
-<select multiple="multiple" name="multi_choice_int" id="id_multi_choice_int" required>
+<select multiple name="multi_choice_int" id="id_multi_choice_int" required>
 <option value="1">ChoiceOption 1</option>
 <option value="2" selected>ChoiceOption 2</option>
 <option value="3" selected>ChoiceOption 3</option>
diff --git a/tests/forms_tests/widget_tests/test_multiwidget.py b/tests/forms_tests/widget_tests/test_multiwidget.py
index f452ad2ad3..bce806231d 100644
--- a/tests/forms_tests/widget_tests/test_multiwidget.py
+++ b/tests/forms_tests/widget_tests/test_multiwidget.py
@@ -155,7 +155,7 @@ class MultiWidgetTest(WidgetTest):
         self.check_html(widget, 'name', 'some text,JP,2007-04-25 06:24:00', html=(
             """
             <input type="text" name="name_0" value="some text" />
-            <select multiple="multiple" name="name_1">
+            <select multiple name="name_1">
                 <option value="J" selected>John</option>
                 <option value="P" selected>Paul</option>
                 <option value="G">George</option>
diff --git a/tests/forms_tests/widget_tests/test_selectmultiple.py b/tests/forms_tests/widget_tests/test_selectmultiple.py
index 149fae6d4b..08606a18c4 100644
--- a/tests/forms_tests/widget_tests/test_selectmultiple.py
+++ b/tests/forms_tests/widget_tests/test_selectmultiple.py
@@ -15,7 +15,7 @@ class SelectMultipleTest(WidgetTest):
 
     def test_render_selected(self):
         self.check_html(self.widget(choices=self.beatles), 'beatles', ['J'], html=(
-            """<select multiple="multiple" name="beatles">
+            """<select multiple name="beatles">
             <option value="J" selected>John</option>
             <option value="P">Paul</option>
             <option value="G">George</option>
@@ -25,7 +25,7 @@ class SelectMultipleTest(WidgetTest):
 
     def test_render_multiple_selected(self):
         self.check_html(self.widget(choices=self.beatles), 'beatles', ['J', 'P'], html=(
-            """<select multiple="multiple" name="beatles">
+            """<select multiple name="beatles">
             <option value="J" selected>John</option>
             <option value="P" selected>Paul</option>
             <option value="G">George</option>
@@ -38,7 +38,7 @@ class SelectMultipleTest(WidgetTest):
         If the value is None, none of the options are selected.
         """
         self.check_html(self.widget(choices=self.beatles), 'beatles', None, html=(
-            """<select multiple="multiple" name="beatles">
+            """<select multiple name="beatles">
             <option value="J">John</option>
             <option value="P">Paul</option>
             <option value="G">George</option>
@@ -52,7 +52,7 @@ class SelectMultipleTest(WidgetTest):
         of the options are selected.
         """
         self.check_html(self.widget(choices=self.beatles), 'beatles', ['John'], html=(
-            """<select multiple="multiple" name="beatles">
+            """<select multiple name="beatles">
             <option value="J">John</option>
             <option value="P">Paul</option>
             <option value="G">George</option>
@@ -65,7 +65,7 @@ class SelectMultipleTest(WidgetTest):
         Multiple options with the same value can be selected (#8103).
         """
         self.check_html(self.widget(choices=self.numeric_choices), 'choices', ['0'], html=(
-            """<select multiple="multiple" name="choices">
+            """<select multiple name="choices">
             <option value="0" selected>0</option>
             <option value="1">1</option>
             <option value="2">2</option>
@@ -80,7 +80,7 @@ class SelectMultipleTest(WidgetTest):
         ones are selected.
         """
         self.check_html(self.widget(choices=self.beatles), 'beatles', ['J', 'G', 'foo'], html=(
-            """<select multiple="multiple" name="beatles">
+            """<select multiple name="beatles">
             <option value="J" selected>John</option>
             <option value="P">Paul</option>
             <option value="G" selected>George</option>
@@ -92,7 +92,7 @@ class SelectMultipleTest(WidgetTest):
         choices = [('1', '1'), ('2', '2'), ('3', '3')]
 
         self.check_html(self.widget(choices=choices), 'nums', [2], html=(
-            """<select multiple="multiple" name="nums">
+            """<select multiple name="nums">
             <option value="1">1</option>
             <option value="2" selected>2</option>
             <option value="3">3</option>
@@ -100,7 +100,7 @@ class SelectMultipleTest(WidgetTest):
         ))
 
         self.check_html(self.widget(choices=choices), 'nums', ['2'], html=(
-            """<select multiple="multiple" name="nums">
+            """<select multiple name="nums">
             <option value="1">1</option>
             <option value="2" selected>2</option>
             <option value="3">3</option>
@@ -108,7 +108,7 @@ class SelectMultipleTest(WidgetTest):
         ))
 
         self.check_html(self.widget(choices=choices), 'nums', [2], html=(
-            """<select multiple="multiple" name="nums">
+            """<select multiple name="nums">
             <option value="1">1</option>
             <option value="2" selected>2</option>
             <option value="3">3</option>
@@ -121,7 +121,7 @@ class SelectMultipleTest(WidgetTest):
             ('Group "1"', (('inner1', 'Inner 1'), ('inner2', 'Inner 2'))),
         ))
         self.check_html(widget, 'nestchoice', ['outer1', 'inner2'], html=(
-            """<select multiple="multiple" name="nestchoice">
+            """<select multiple name="nestchoice">
             <option value="outer1" selected>Outer 1</option>
             <optgroup label="Group &quot;1&quot;">
             <option value="inner1">Inner 1</option>
diff --git a/tests/model_forms/tests.py b/tests/model_forms/tests.py
index 7af2aff825..b6ce55cf40 100644
--- a/tests/model_forms/tests.py
+++ b/tests/model_forms/tests.py
@@ -1168,7 +1168,7 @@ class ModelFormBasicTests(TestCase):
 <option value="%s">Mike Royko</option>
 </select></li>
 <li>Article: <textarea rows="10" cols="40" name="article" required></textarea></li>
-<li>Categories: <select multiple="multiple" name="categories">
+<li>Categories: <select multiple name="categories">
 <option value="%s" selected>Entertainment</option>
 <option value="%s" selected>It&#39;s a test</option>
 <option value="%s">Third test</option>
@@ -1210,7 +1210,7 @@ class ModelFormBasicTests(TestCase):
 <option value="%s" selected>Mike Royko</option>
 </select></li>
 <li>Article: <textarea rows="10" cols="40" name="article" required>Hello.</textarea></li>
-<li>Categories: <select multiple="multiple" name="categories">
+<li>Categories: <select multiple name="categories">
 <option value="%s">Entertainment</option>
 <option value="%s">It&#39;s a test</option>
 <option value="%s">Third test</option>
@@ -1258,7 +1258,7 @@ class ModelFormBasicTests(TestCase):
             """<li><label for="id_headline">Headline:</label>
 <input id="id_headline" type="text" name="headline" maxlength="50" required /></li>
 <li><label for="id_categories">Categories:</label>
-<select multiple="multiple" name="categories" id="id_categories">
+<select multiple name="categories" id="id_categories">
 <option value="%d" selected>Entertainment</option>
 <option value="%d" selected>It&39;s a test</option>
 <option value="%d">Third test</option>
@@ -1327,7 +1327,7 @@ class ModelFormBasicTests(TestCase):
 <option value="%s">Mike Royko</option>
 </select></td></tr>
 <tr><th>Article:</th><td><textarea rows="10" cols="40" name="article" required></textarea></td></tr>
-<tr><th>Categories:</th><td><select multiple="multiple" name="categories">
+<tr><th>Categories:</th><td><select multiple name="categories">
 <option value="%s">Entertainment</option>
 <option value="%s">It&#39;s a test</option>
 <option value="%s">Third test</option>
@@ -1357,7 +1357,7 @@ class ModelFormBasicTests(TestCase):
 <option value="%s" selected>Mike Royko</option>
 </select></li>
 <li>Article: <textarea rows="10" cols="40" name="article" required>Hello.</textarea></li>
-<li>Categories: <select multiple="multiple" name="categories">
+<li>Categories: <select multiple name="categories">
 <option value="%s" selected>Entertainment</option>
 <option value="%s">It&#39;s a test</option>
 <option value="%s">Third test</option>
@@ -1501,7 +1501,7 @@ class ModelFormBasicTests(TestCase):
 <option value="%s">Mike Royko</option>
 </select></li>
 <li>Article: <textarea rows="10" cols="40" name="article" required></textarea></li>
-<li>Categories: <select multiple="multiple" name="categories">
+<li>Categories: <select multiple name="categories">
 <option value="%s">Entertainment</option>
 <option value="%s">It&#39;s a test</option>
 <option value="%s">Third test</option>
@@ -1527,7 +1527,7 @@ class ModelFormBasicTests(TestCase):
 <option value="%s">Mike Royko</option>
 </select></li>
 <li>Article: <textarea rows="10" cols="40" name="article" required></textarea></li>
-<li>Categories: <select multiple="multiple" name="categories">
+<li>Categories: <select multiple name="categories">
 <option value="%s">Entertainment</option>
 <option value="%s">It&#39;s a test</option>
 <option value="%s">Third test</option>
@@ -2681,7 +2681,7 @@ class OtherModelFormTests(TestCase):
             form.as_p(),
             """<p><label for="id_name">Name:</label> <input id="id_name" type="text" name="name" maxlength="50" required /></p>
         <p><label for="id_colours">Colours:</label>
-        <select multiple="multiple" name="colours" id="id_colours" required>
+        <select multiple name="colours" id="id_colours" required>
         <option value="%(blue_pk)s">Blue</option>
         </select></p>"""
             % {'blue_pk': colour.pk})