Programmatically Insert WordPress Post Categories

insert_wp_post_category.php

<?php
/**
 * Insert a new Post Category
 */
function example_insert_category() {
	wp_insert_term(
		'Example Category',
		'category',
		array(
		  'description'	=> 'This is an example category created with wp_insert_term.',
		  'slug' 		=> 'example-category'
		)
	);
}
add_action( 'after_setup_theme', 'example_insert_category' );