Police are looking for a man who sexually assaulted a woman at a Collingwood nightclub.

A man approached a Camberwell woman, 22, about 3am at a nightclub on Wellington Street, police said.

He lifted her skirt and sexually assaulted her on 26 January.

The Melbourne Sexual Offence and Child Abuse Investigation Team asked witnesses to come forward, releasing photos of the man.

They described him as Middle Eastern in appearance, aged 24 to 25-years-old, and about 188cm tall with an olive complexion.

He wore a brown t-shirt, blue jeans and runners at the time of the incident.