diff --git a/core/config/schema/core.data_types.schema.yml b/core/config/schema/core.data_types.schema.yml
index cc89fa9..55de923 100644
--- a/core/config/schema/core.data_types.schema.yml
+++ b/core/config/schema/core.data_types.schema.yml
@@ -445,6 +445,9 @@ field.storage_settings.string:
     case_sensitive:
       type: boolean
       label: 'Case sensitive'
+    ascii:
+      type: boolean
+      label: 'US ASCII characters only'
 
 field.field_settings.string:
   type: mapping
diff --git a/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
index d0aba49..0f7f57b 100644
--- a/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
+++ b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
@@ -144,6 +144,9 @@ protected function createFieldSql($name, $spec) {
       if (!empty($spec['binary'])) {
         $sql .= ' BINARY';
       }
+      if (!empty($spec['ascii'])) {
+        $sql .= ' CHARACTER SET ascii COLLATE ascii_general_ci';
+      }
     }
     elseif (isset($spec['precision']) && isset($spec['scale'])) {
       $sql .= '(' . $spec['precision'] . ', ' . $spec['scale'] . ')';
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
index 8817c87..ba7e788 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/StringItem.php
@@ -32,6 +32,7 @@ class StringItem extends StringItemBase {
   public static function defaultStorageSettings() {
     return array(
       'max_length' => 255,
+      'ascii' => FALSE,
     ) + parent::defaultStorageSettings();
   }
 
@@ -45,6 +46,7 @@ public static function schema(FieldStorageDefinitionInterface $field_definition)
           'type' => 'varchar',
           'length' => (int) $field_definition->getSetting('max_length'),
           'binary' => $field_definition->getSetting('case_sensitive'),
+          'ascii' => $field_definition->getSetting('ascii'),
         ),
       ),
     );
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UuidItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UuidItem.php
index e787029..02eaebe 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UuidItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UuidItem.php
@@ -29,6 +29,7 @@ class UuidItem extends StringItem {
   public static function defaultStorageSettings() {
     return array(
       'max_length' => 128,
+      'ascii' => TRUE,
     ) + parent::defaultStorageSettings();
   }
 
diff --git a/core/modules/menu_link_content/src/Entity/MenuLinkContent.php b/core/modules/menu_link_content/src/Entity/MenuLinkContent.php
index 5570a2a..b48e985 100644
--- a/core/modules/menu_link_content/src/Entity/MenuLinkContent.php
+++ b/core/modules/menu_link_content/src/Entity/MenuLinkContent.php
@@ -250,6 +250,7 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
       ->setLabel(t('Bundle'))
       ->setDescription(t('The content menu link bundle.'))
       ->setSetting('max_length', EntityTypeInterface::BUNDLE_MAX_LENGTH)
+      ->setSetting('ascii', TRUE)
       ->setReadOnly(TRUE);
 
     $fields['title'] = BaseFieldDefinition::create('string')
@@ -291,7 +292,8 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
     $fields['menu_name'] = BaseFieldDefinition::create('string')
       ->setLabel(t('Menu name'))
       ->setDescription(t('The menu name. All links with the same menu name (such as "tools") are part of the same menu.'))
-      ->setDefaultValue('tools');
+      ->setDefaultValue('tools')
+      ->setSetting('ascii', TRUE);
 
     $fields['link'] = BaseFieldDefinition::create('link')
       ->setLabel(t('Link'))
diff --git a/core/modules/system/src/Tests/Database/SchemaTest.php b/core/modules/system/src/Tests/Database/SchemaTest.php
index a59b9d9..8bb22a0 100644
--- a/core/modules/system/src/Tests/Database/SchemaTest.php
+++ b/core/modules/system/src/Tests/Database/SchemaTest.php
@@ -49,6 +49,12 @@ function testSchema() {
           'default' => "'\"funky default'\"",
           'description' => 'Schema column description for string.',
         ),
+        'test_field_string_ascii'  => array(
+          'type' => 'varchar',
+          'length' => 255,
+          'ascii' => TRUE,
+          'description' => 'Schema column description for ASCII string.',
+        ),
       ),
     );
     db_create_table('test_table', $table_specification);
@@ -62,6 +68,17 @@ function testSchema() {
     // Assert that the column comment has been set.
     $this->checkSchemaComment($table_specification['fields']['test_field']['description'], 'test_table', 'test_field');
 
+    // Make sure that varchard fields have the correct collation.
+    $columns = db_query('SHOW FULL COLUMNS FROM {test_table}');
+    foreach ($columns as $column) {
+      if ($column->Field == 'test_field_string') {
+        $this->assertTrue($column->Collation == 'utf8_general_ci');
+      }
+      if ($column->Field == 'test_field_string_ascii') {
+        $this->assertTrue($column->Collation == 'ascii_general_ci');
+      }
+    }
+
     // An insert without a value for the column 'test_table' should fail.
     $this->assertFalse($this->tryInsert(), 'Insert without a default failed.');