She was attacked in St Vincent Street at around 9.35pm on Tuesday.
Officers are appealing for witnesses and want to identify and speak to the men in these CCTV photographs.
Both images were captured on CCTV inside city centre pub, The Goose, in Union Street.
The first picture shows a man wearing blue jeans, dark jacket and blue and white shoes.
The other shows a man wearing a dark grey jacket.
Police said: "Detectives are eager to speak to anyone who recognises the men in the images."