I have many duplicate songs in my iTunes. Is there a way to quickly delete all duplicates without having to manually delete all of them?

How to find and remove duplicate items in your iTunes library - http://support.apple.com/kb/HT2905

http://dougscripts.com/itunes/itinfo/dupin.php (commercial)

post by turingtest2 - https://discussions.apple.com/thread/3555601 - different types of duplicates and techniques

http://www.araxis.com/find-duplicate-files (commercial, free trial) - finds duplicate files on computer, not specifically iTunes

I would do it manually. As you can see from turingtest2's post, some duplicates are not really duplicates.

I would also review how you add media to iTunes. It should not be producing all that many duplicates.