Officers released CCTV images of a man they think can help with their inquiries into the attack, which happened at about 11pm on Saturday, May 15.
He is white, with short, fair hair and a heavy build.
He was wearing a light grey hooded top, black combat trousers and blue trainers. He was also carrying a white plastic bag.
Detective Constable Leigh-Ann Sutherland, of Helen Street Police Station, said: “There was a large crowd gathered in George Square at the time of this assault and I am appealing to anyone who saw what happened to get in touch.
“The man in the image, or anyone who can help with inquiries, is asked to call Police Scotland on 101, quoting incident number 1055 of Saturday May 15.”