Is purgatory real or myth?

This is a good question but in all reality we simply do not know, it's simply what we are taught and either we believe in it or we don't.

Philosophically it could be either, real or myth. The fact we have no empirical knowledge of its existence. However, it have been written about widely more so in Catholicism. There's a book of the same name if interested to do some reading on the subject.

Purgatory is a myth. God is a myth. Hell is a myth. Satan is a myth.