The incident is alleged to have taken place in West Park, Hull in the early hours of Saturday, February 9 2019.
The victim had been drinking with friends on the evening of Friday, February 8 in the New Griffin pub on Anlaby Road when she was approached by a man who engaged her and her friends in conversation.
The man appeared to be drinking alone in the pub.
When the victim left the pub, she walked down Anlaby Road towards the city centre and it is believed the man followed her.
As the woman reached the junction of Anlaby Road and Walton Street, she entered West Park where she was allegedly attacked and raped.
Crimestoppers have described the suspect in the case as speaking with a foreign accent.
They said: "He had tanned skin, is aged in his mid-twenties and is approximately 5ft 8in to 5ft 10in tall with a proportionate build.
"At the time of the incident the suspect had dark hair and some facial hair."
A spokesman for the charity said: “The victim has been through a horrific ordeal and we are appealing to anybody who may have information on this attack to contact us, with the promise that you will remain completely anonymous.
“If you have any information regarding this man’s whereabouts or any information at all, please do the right thing and contact us.
"In over 30 years we have always kept our promise of 100% anonymity to everyone who trusts our charity with their crime information.
“Remember that your information could help keep someone safe from future harm.
"Our UK Contact Centre is open 24/7 on 0800 555 111 or you can use our anonymous online form.
"No-one will know you contacted us, and it could be your information that makes a huge difference.”
Information passed directly to the police will not qualify for the reward, only that passed to the charity directly.