Officers want to speak to the man pictured following the alleged offence between 06.30am and 07.15am in an alleyway off Bolton Road near to the Broadway Shopping Centre and the Corn Dolly pub.
It is thought that after the assault, the victim approached a number of people and police are appealing for anyone who saw a woman in distress to come forward.
A man officers want to speak to in connection with the offence is described as white, aged 20 to 25, of slim build and around 5ft 10ins tall.
He had blonde hair and was wearing a black hooded top, blue ripped jeans and dark shoes.
It is thought he may have been picked up by a taxi following the incident, police said in their appeal.
Detective Inspector Claire Smith, of the Bradford Safeguarding Unit, said: “I would appeal to anyone who witnessed this incident, recognises the man pictured or who may have been approached by the victim to come forward.”
Anyone with information is asked to call police on 101, quoting the log number 13180188422.