diff --git a/core/includes/form.inc b/core/includes/form.inc
index 926b149d967889ae29831449b517d5ebbaf49d90..0add7ccc5f03bc421786bfb439836fc4e4020b03 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -275,18 +275,6 @@ function drupal_process_form($form_id, &$form, &$form_state) {
   \Drupal::formBuilder()->processForm($form_id, $form, $form_state);
 }
 
-/**
- * Prepares a structured form array.
- *
- * @deprecated in Drupal 8.x-dev, will be removed before Drupal 8.0.
- *   Use \Drupal::formBuilder()->prepareForm().
- *
- * @see \Drupal\Core\Form\FormBuilderInterface::prepareForm().
- */
-function drupal_prepare_form($form_id, &$form, &$form_state) {
-  \Drupal::formBuilder()->prepareForm($form_id, $form, $form_state);
-}
-
 /**
  * Validates user-submitted form data in the $form_state array.
  *
diff --git a/core/modules/field/src/Tests/FieldAttachOtherTest.php b/core/modules/field/src/Tests/FieldAttachOtherTest.php
index 8e54bc1f5a0bdee4f4a0975027b59f29cd41732f..5046b1d7917c343bf90826b0199f3755600d4386 100644
--- a/core/modules/field/src/Tests/FieldAttachOtherTest.php
+++ b/core/modules/field/src/Tests/FieldAttachOtherTest.php
@@ -342,7 +342,7 @@ function testEntityFormDisplayExtractFormValues() {
     $values_2[1]['value'] = 0;
 
     // Pretend the form has been built.
-    drupal_prepare_form('field_test_entity_form', $form, $form_state);
+    \Drupal::formBuilder()->prepareForm('field_test_entity_form', $form, $form_state);
     drupal_process_form('field_test_entity_form', $form, $form_state);
     $form_state['values'][$this->field_name] = $values;
     $form_state['values'][$this->field_name_2] = $values_2;
diff --git a/core/modules/system/src/Tests/Form/ElementsTableSelectTest.php b/core/modules/system/src/Tests/Form/ElementsTableSelectTest.php
index e6bfddaf61a6fae93f987a1aa89fc5503214c067..47435f6768348f6964c334c0d6c151bfea9c7257 100644
--- a/core/modules/system/src/Tests/Form/ElementsTableSelectTest.php
+++ b/core/modules/system/src/Tests/Form/ElementsTableSelectTest.php
@@ -217,7 +217,7 @@ private function formSubmitHelper($form, $edit) {
     $form_state['input'] = $edit;
     $form_state['input']['form_id'] = $form_id;
 
-    drupal_prepare_form($form_id, $form, $form_state);
+    \Drupal::formBuilder()->prepareForm($form_id, $form, $form_state);
 
     drupal_process_form($form_id, $form, $form_state);
 
diff --git a/core/modules/system/src/Tests/Form/FormTest.php b/core/modules/system/src/Tests/Form/FormTest.php
index a380bd79c71c9706f7cf847bb5f5b8d58d0ffeed..a82943ecec145f31461c57034ea5dd90bf6b872f 100644
--- a/core/modules/system/src/Tests/Form/FormTest.php
+++ b/core/modules/system/src/Tests/Form/FormTest.php
@@ -112,7 +112,7 @@ function testRequiredFields() {
           // The form token CSRF protection should not interfere with this test,
           // so we bypass it by setting the token to FALSE.
           $form['#token'] = FALSE;
-          drupal_prepare_form($form_id, $form, $form_state);
+          \Drupal::formBuilder()->prepareForm($form_id, $form, $form_state);
           drupal_process_form($form_id, $form, $form_state);
           $errors = form_get_errors($form_state);
           // Form elements of type 'radios' throw all sorts of PHP notices
diff --git a/core/modules/system/system.api.php b/core/modules/system/system.api.php
index 857145b1ca0ae66c3395f07683067666589edb04..8ff4b544eef066857f46df75d523c83ce04989a1 100644
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -740,7 +740,7 @@ function hook_form_alter(&$form, &$form_state, $form_id) {
  *
  * @see hook_form_alter()
  * @see hook_form_BASE_FORM_ID_alter()
- * @see drupal_prepare_form()
+ * @see \Drupal\Core\Form\FormBuilderInterface::prepareForm()
  * @see forms_api_reference.html
  */
 function hook_form_FORM_ID_alter(&$form, &$form_state, $form_id) {
@@ -786,7 +786,7 @@ function hook_form_FORM_ID_alter(&$form, &$form_state, $form_id) {
  *
  * @see hook_form_alter()
  * @see hook_form_FORM_ID_alter()
- * @see drupal_prepare_form()
+ * @see \Drupal\Core\Form\FormBuilderInterface::prepareForm()
  */
 function hook_form_BASE_FORM_ID_alter(&$form, &$form_state, $form_id) {
   // Modification for the form with the given BASE_FORM_ID goes here. For