diff --git a/assets/src/js/_acf-field-select.js b/assets/src/js/_acf-field-select.js
index 5d9a23e6..61146a40 100644
--- a/assets/src/js/_acf-field-select.js
+++ b/assets/src/js/_acf-field-select.js
@@ -37,6 +37,7 @@
 					multiple: this.get( 'multiple' ),
 					placeholder: this.get( 'placeholder' ),
 					allowNull: this.get( 'allow_null' ),
+					tags: this.get( 'create_options' ),
 					ajaxAction: ajaxAction,
 				} );
 			}
diff --git a/assets/src/js/_acf-select2.js b/assets/src/js/_acf-select2.js
index 620a3acd..0c5f3a3e 100644
--- a/assets/src/js/_acf-select2.js
+++ b/assets/src/js/_acf-select2.js
@@ -19,6 +19,7 @@
 			multiple: false,
 			field: false,
 			ajax: false,
+			tags: false,
 			ajaxAction: '',
 			ajaxData: function ( data ) {
 				return data;
@@ -220,7 +221,6 @@
 				if ( field.get( 'nonce' ) ) {
 					ajaxData.nonce = field.get( 'nonce' );
 				}
-
 			}
 
 			// callback
@@ -324,6 +324,11 @@
 				data: [],
 			};
 
+			if ( this.get( 'tags' ) ) {
+				options.tags = true;
+				options.tokenSeparators = [ ',' ];
+			}
+
 			// Clear empty templateSelections, templateResults, or dropdownCssClass.
 			if ( ! options.templateSelection ) {
 				delete options.templateSelection;
diff --git a/includes/fields/class-acf-field-select.php b/includes/fields/class-acf-field-select.php
index a6238ea2..bd9f810b 100644
--- a/includes/fields/class-acf-field-select.php
+++ b/includes/fields/class-acf-field-select.php
@@ -27,14 +27,16 @@ function initialize() {
 			$this->doc_url       = 'https://developer.wordpress.org/secure-custom-fields/features/fields/select/';
 			$this->tutorial_url  = 'https://developer.wordpress.org/secure-custom-fields/features/fields/select/select-tutorial/';
 			$this->defaults      = array(
-				'multiple'      => 0,
-				'allow_null'    => 0,
-				'choices'       => array(),
-				'default_value' => '',
-				'ui'            => 0,
-				'ajax'          => 0,
-				'placeholder'   => '',
-				'return_format' => 'value',
+				'multiple'       => 0,
+				'allow_null'     => 0,
+				'choices'        => array(),
+				'default_value'  => '',
+				'ui'             => 0,
+				'ajax'           => 0,
+				'placeholder'    => '',
+				'return_format'  => 'value',
+				'create_options' => 0,
+				'save_options'   => 0,
 			);
 
 			// ajax
@@ -204,38 +206,35 @@ public function get_ajax_query( $options = array() ) {
 
 
 		/**
-		 * Create the HTML interface for your field
+		 * Creates the HTML interface for the field.
 		 *
-		 * @param   $field - an array holding all the field's data
+		 * @param array $field An array holding all the field's data.
+		 * @return  void
 		 *
-		 * @type    action
 		 * @since   ACF 3.6
-		 * @date    23/01/13
 		 */
 		function render_field( $field ) {
 
-			// convert
 			$value   = acf_get_array( $field['value'] );
 			$choices = acf_get_array( $field['choices'] );
 
-			// placeholder
 			if ( empty( $field['placeholder'] ) ) {
 				$field['placeholder'] = _x( 'Select', 'verb', 'secure-custom-fields' );
 			}
 
-			// add empty value (allows '' to be selected)
+			// Add empty value (allows '' to be selected).
 			if ( empty( $value ) ) {
 				$value = array( '' );
 			}
 
-			// prepend empty choice
+			// Prepend empty choice
 			// - only for single selects
 			// - have tried array_merge but this causes keys to re-index if is numeric (post ID's)
 			if ( isset( $field['allow_null'] ) && $field['allow_null'] && isset( $field['multiple'] ) && ! $field['multiple'] ) {
 				$choices = array( '' => "- {$field['placeholder']} -" ) + $choices;
 			}
 
-			// clean up choices if using ajax
+			// Clean up choices if using ajax.
 			if ( isset( $field['ui'] ) && $field['ui'] && isset( $field['ajax'] ) && $field['ajax'] ) {
 				$minimal = array();
 				foreach ( $value as $key ) {
@@ -246,7 +245,6 @@ function render_field( $field ) {
 				$choices = $minimal;
 			}
 
-			// vars
 			$select = array(
 				'id'               => acf_maybe_get( $field, 'id', '' ),
 				'class'            => acf_maybe_get( $field, 'class', '' ),
@@ -262,7 +260,6 @@ function render_field( $field ) {
 				$select['aria-label'] = $field['aria-label'];
 			}
 
-			// multiple
 			if ( isset( $field['multiple'] ) && $field['multiple'] ) {
 				$select['multiple'] = 'multiple';
 				$select['size']     = 5;
@@ -274,6 +271,10 @@ function render_field( $field ) {
 				}
 			}
 
+			if ( ! empty( $field['create_options'] ) && $field['ui'] ) {
+				$select['data-create_options'] = true;
+			}
+
 			// special atts
 			if ( ! empty( $field['readonly'] ) ) {
 				$select['readonly'] = 'readonly';
@@ -308,22 +309,33 @@ function render_field( $field ) {
 			$select['value']   = $value;
 			$select['choices'] = $choices;
 
+			if ( ! empty( $field['create_options'] ) && $field['ui'] && is_array( $field['value'] ) ) {
+				foreach ( $field['value'] as $value ) {
+					// Already exists in choices.
+					if ( isset( $field['choices'][ $value ] ) ) {
+						continue;
+					}
+
+					$option = esc_attr( $value );
+
+					$select['choices'][ $option ] = $option;
+				}
+			}
+
 			// render
 			acf_select_input( $select );
 		}
 
 
 		/**
-		 * Create extra options for your field. This is rendered when editing a field.
-		 * The value of $field['name'] can be used (like bellow) to save extra data to the $field
+		 * Renders the field settings used in the "General" tab.
 		 *
-		 * @type    action
-		 * @since   ACF 3.6
-		 * @date    23/01/13
+		 * @since ACF 3.6
 		 *
-		 * @param   $field  - an array holding all the field's data
+		 * @param array $field An array holding all the field's data.
+		 * @return void
 		 */
-		function render_field_settings( $field ) {
+		public function render_field_settings( $field ) {
 
 			// encode choices (convert from array)
 			$field['choices']       = acf_encode_choices( $field['choices'] );
@@ -388,7 +400,7 @@ function render_field_settings( $field ) {
 		 * @param array $field The field settings array.
 		 * @return void
 		 */
-		function render_field_validation_settings( $field ) {
+		public function render_field_validation_settings( $field ) {
 			acf_render_field_setting(
 				$field,
 				array(
@@ -409,7 +421,7 @@ function render_field_validation_settings( $field ) {
 		 * @param array $field The field settings array.
 		 * @return void
 		 */
-		function render_field_presentation_settings( $field ) {
+		public function render_field_presentation_settings( $field ) {
 			acf_render_field_setting(
 				$field,
 				array(
@@ -436,21 +448,70 @@ function render_field_presentation_settings( $field ) {
 					),
 				)
 			);
+
+			acf_render_field_setting(
+				$field,
+				array(
+					'label'        => __( 'Create Options', 'secure-custom-fields' ),
+					'instructions' => __( 'Allow content editors to create new options by typing in the Select input. Multiple options can be created from a comma separated string.', 'secure-custom-fields' ),
+					'name'         => 'create_options',
+					'type'         => 'true_false',
+					'ui'           => 1,
+					'conditions'   => array(
+						array(
+							'field'    => 'ui',
+							'operator' => '==',
+							'value'    => 1,
+						),
+						array(
+							'field'    => 'multiple',
+							'operator' => '==',
+							'value'    => 1,
+						),
+					),
+				)
+			);
+
+			acf_render_field_setting(
+				$field,
+				array(
+					'label'        => __( 'Save Options', 'secure-custom-fields' ),
+					'instructions' => __( 'Save created options back to the "Choices" setting in the field definition.', 'secure-custom-fields' ),
+					'name'         => 'save_options',
+					'type'         => 'true_false',
+					'ui'           => 1,
+					'conditions'   => array(
+						array(
+							'field'    => 'ui',
+							'operator' => '==',
+							'value'    => 1,
+						),
+						array(
+							'field'    => 'multiple',
+							'operator' => '==',
+							'value'    => 1,
+						),
+						array(
+							'field'    => 'create_options',
+							'operator' => '==',
+							'value'    => 1,
+						),
+					),
+				)
+			);
 		}
 
 		/**
-		 * This filter is applied to the $value after it is loaded from the db
+		 * Filters the $value after it is loaded from the db.
 		 *
-		 * @type    filter
-		 * @since   ACF 3.6
-		 * @date    23/01/13
+		 * @since ACF 3.6
 		 *
-		 * @param   $value (mixed) the value found in the database
-		 * @param   $post_id (mixed) the post_id from which the value was loaded
-		 * @param   $field (array) the field array holding all the field options
-		 * @return  $value
+		 * @param mixed          $value   The value found in the database.
+		 * @param integer|string $post_id The post_id from which the value was loaded.
+		 * @param array          $field   The field array holding all the field options.
+		 * @return mixed
 		 */
-		function load_value( $value, $post_id, $field ) {
+		public function load_value( $value, $post_id, $field ) {
 
 			// Return an array when field is set for multiple.
 			if ( $field['multiple'] ) {
@@ -466,21 +527,16 @@ function load_value( $value, $post_id, $field ) {
 
 
 		/**
+		 * Filters the $field before it is saved to the database.
 		 *
-		 * This filter is applied to the $field before it is saved to the database
-		 *
-		 * @type    filter
-		 * @since   ACF 3.6
-		 * @date    23/01/13
-		 *
-		 * @param   $field - the field array holding all the field options
-		 * @param   $post_id - the field group ID (post_type = acf)
+		 * @since ACF 3.6
 		 *
-		 * @return  $field - the modified field
+		 * @param array $field The field array holding all the field options.
+		 * @return array
 		 */
-		function update_field( $field ) {
+		public function update_field( $field ) {
 
-			// decode choices (convert to array)
+			// Decode choices (convert to array).
 			$field['choices']       = acf_decode_choices( $field['choices'] );
 			$field['default_value'] = acf_decode_choices( $field['default_value'], true );
 
@@ -489,25 +545,22 @@ function update_field( $field ) {
 				$field['default_value'] = acf_unarray( $field['default_value'] );
 			}
 
-			// return
 			return $field;
 		}
 
 
 		/**
-		 * This filter is applied to the $value before it is updated in the db
+		 * Filters the $value before it is updated in the db.
 		 *
-		 * @type    filter
-		 * @since   ACF 3.6
-		 * @date    23/01/13
+		 * @since ACF 3.6
 		 *
-		 * @param   $value - the value which will be saved in the database
-		 * @param   $post_id - the post_id of which the value will be saved
-		 * @param   $field - the field array holding all the field options
+		 * @param mixed          $value   The value which will be saved in the database.
+		 * @param integer|string $post_id The post_id of which the value will be saved.
+		 * @param array          $field   The field array holding all the field options.
 		 *
-		 * @return  $value - the modified value
+		 * @return mixed
 		 */
-		function update_value( $value, $post_id, $field ) {
+		public function update_value( $value, $post_id, $field ) {
 
 			// Bail early if no value.
 			if ( empty( $value ) ) {
@@ -520,45 +573,64 @@ function update_value( $value, $post_id, $field ) {
 				$value = array_map( 'strval', $value );
 			}
 
-			// return
+			// Save custom options back to the field definition if configured.
+			if ( ! empty( $field['save_options'] ) && is_array( $value ) ) {
+				// Get the raw field, using the ID if present or the key otherwise (i.e. when using JSON).
+				$selector = $field['ID'] ? $field['ID'] : $field['key'];
+				$field    = acf_get_field( $selector );
+
+				// Bail if we don't have a valid field or field ID (JSON only).
+				if ( empty( $field['ID'] ) ) {
+					return $value;
+				}
+
+				foreach ( $value as $v ) {
+					// Ignore if the option already exists.
+					if ( isset( $field['choices'][ $v ] ) ) {
+						continue;
+					}
+
+					// Unslash (fixes serialize single quote issue) and sanitize.
+					$v = wp_unslash( $v );
+					$v = sanitize_text_field( $v );
+
+					// Append to the field choices.
+					$field['choices'][ $v ] = $v;
+				}
+
+				acf_update_field( $field );
+			}
 			return $value;
 		}
 
 
 		/**
-		 * This function will translate field settings
+		 * Translates the field settings.
 		 *
-		 * @type    function
-		 * @date    8/03/2016
-		 * @since   ACF 5.3.2
+		 * @since ACF 5.3.2
 		 *
-		 * @param   $field (array)
-		 * @return  $field
+		 * @param array $field The main field array.
+		 * @return array
 		 */
-		function translate_field( $field ) {
+		public function translate_field( $field ) {
 
-			// translate
 			$field['choices'] = acf_translate( $field['choices'] );
-
-			// return
 			return $field;
 		}
 
 
 		/**
-		 * This filter is applied to the $value after it is loaded from the db and before it is returned to the template
+		 * Filters the $value after it is loaded from the db, and before it is returned to the template.
 		 *
-		 * @type    filter
-		 * @since   ACF 3.6
-		 * @date    23/01/13
+		 * @since ACF 3.6
 		 *
-		 * @param   $value (mixed) the value which was loaded from the database
-		 * @param   $post_id (mixed) the post_id from which the value was loaded
-		 * @param   $field (array) the field array holding all the field options
+		 * @param mixed          $value   The value which was loaded from the database.
+		 * @param integer|string $post_id The post_id from which the value was loaded.
+		 * @param array          $field   The field array holding all the field options.
 		 *
-		 * @return  $value (mixed) the modified value
+		 * @return mixed
 		 */
-		function format_value( $value, $post_id, $field ) {
+		public function format_value( $value, $post_id, $field ) {
 			if ( is_array( $value ) ) {
 				foreach ( $value as $i => $val ) {
 					$value[ $i ] = $this->format_value_single( $val, $post_id, $field );
@@ -569,35 +641,33 @@ function format_value( $value, $post_id, $field ) {
 			return $value;
 		}
 
-
-		function format_value_single( $value, $post_id, $field ) {
-
-			// bail early if is empty
+		/**
+		 * Formats the value when the select is not a multi-select.
+		 *
+		 * @since 3.6
+		 *
+		 * @param mixed          $value   The value to format.
+		 * @param integer|string $post_id The post_id from which the value was loaded.
+		 * @param array          $field   The field array holding all the field options.
+		 * @return mixed
+		 */
+		public function format_value_single( $value, $post_id, $field ) {
+			// Bail early if is empty.
 			if ( acf_is_empty( $value ) ) {
 				return $value;
 			}
 
-			// vars
 			$label = acf_maybe_get( $field['choices'], $value, $value );
 
-			// value
-			$return_format = isset( $field['return_format'] ) ? $field['return_format'] : 'value';
-
-			if ( 'value' === $return_format ) {
-				// do nothing
-				return $value;
-			} elseif ( 'label' === $return_format ) {
-				// label
+			if ( 'label' === $field['return_format'] ) {
 				$value = $label;
-			} elseif ( 'array' === $return_format ) {
-				// array
+			} elseif ( 'array' === $field['return_format'] ) {
 				$value = array(
 					'value' => $value,
 					'label' => $label,
 				);
 			}
 
-			// return
 			return $value;
 		}