An 18-year-old woman was sexually assaulted as she walked through Cheltenham.
A Gloucestershire Police spokesman said the attack happened in the early hours in an alleyway next to the Thirteen Degrees night club in St George's Road.
"The woman was assaulted by a man who then walked off past Charles Takeaway in Royal Well Place in the early hours of Wednesday," he said.
The offender is described as white, aged about 20, and of skinny build.
He was with another man, around the same age and with black hair.
Police urged anyone who was in the area at about 0120 GMT to contact them or Crimestoppers.