Remove Categories Box From WordPress Post Editor

Remove the ‘Categories’ box from the ‘Add New Post’ editor in WordPress. Drop this into your theme’s functions.php file.

add_action( 'add_meta_boxes', 'isa_remove_categories_meta_box' );
function isa_remove_categories_meta_box() {
    
    remove_meta_box( 'categorydiv', 'post', 'side' );// remove the Categories box
    
    // you can remove more boxes here
    // for example...
    // 	remove_meta_box( 'formatdiv', 'post', 'side' ); // remove the Format box
    //	remove_meta_box( 'tagsdiv-post_tag', 'post', 'side' );// remove the Tags box
 
}