User blog comment:Zathronas/Analysis by an Author: Over-analyzing/@comment-6830001-20131223010850/@comment-3146930-20131223021135

Think about it. Ozpin's title at the school is Headmaster; this may not seem like a lot, but if Ozpin was a girl, he would be the Headmistress. Plus look at the way Ozpin dresses, always being seen in a suit while most female characters where dresses or some other attire suited toward females. Plus there is a blink-and-you'll-miss-it part in Episode 10 (The Badge and The Burden, Pt.2) where Peter Port says "I've believed in Professor Ozpin for many years, and the man's never once led me astray!"

He clearly calls Professor Ozpin a man. I think that this proves that Ozpin is in fact, male.