Age question.

Can I publish an game on steam if I am 15 years old?(16 in august)

This is more than likely a Steam submission guidelines question that would be better addressed by Steam, but in my opinion to enter into a business arrangement you will most likely need to be of legal age to enter into the contract. Like I said though you should check Steam submission/forums for an answer instead of here…you are more likely to get a solid answer from them.