Remove Post Tags from WordPress Admin

Remove from Posts sub menu in left side WordPress Admin Menu:

function unbox_change_menus () {
  remove_submenu_page( 'edit.php', 'edit-tags.php?taxonomy=post_tag' );
}
add_action('admin_menu', 'unbox_change_menus');

Remove Tags column from List of Posts in Admin:

add_filter('manage_posts_columns', 'unbox_custom_columns_posts');
function unbox_custom_columns_posts( $defaults ) {
    unset($defaults['tags']); //remove tags
    return $defaults;
}

Remove Tags Side Box when editing/creating post:

function unbox_remove_my_post_metaboxes() {
    remove_meta_box( 'tagsdiv-post_tag', 'post', 'side'); 
}
add_action('admin_menu', 'unbox_remove_my_post_metaboxes');