Create a new category in WordPress

/**
 * Creates a new category.
 * Note the `admin_init` action.
 *
 * @see https://wpcodebook.com/wordpress-create-new-category/
 * @see https://developer.wordpress.org/reference/functions/wp_create_category/
 */
add_action( 'admin_init', function () {
	wp_create_category( 'My category' );
} );