Greater Manchester Police (GMP) have said that reports of male rape have more than doubled in the city in the last 12 months.
Since April 2014, men have been victims of 84 incidents of rape or attempted rape, compared to 35 in the previous 12 months.
Sexual assaults on men have also risen, from 69 to 93 in the same periods.
GMP and Survivors Manchester, a group that helps men who have been raped or sexually abused, have launched a poster campaign aimed at men who have been the victims of rape, urging them to come forward and break the silence.
Police believe that many incidents go unreported by victims.
Detective Inspector Damian Simpson from GMP's Serious Sexual Offences Unit said: "Rape is a difficult subject to talk about and we appreciate that coming forward is never easy."
"We know that male rape is heavily under-reported and want to reach out to men and let them know that help is available."
"As the poster says, we're here for you and will never judge you."
According to a 2012 poll carried out by Mumsnet, 83 per cent of women who had been raped did not report it to the police - the figure amongst men is thought to be even higher.
Duncan Craig, CEO and psychotherapist at said: "We need to work together to break the silence that surrounds the rape and sexual assault of men, so those affected can get the support they deserve."
The posters feature volunteers who put themselves forward to appear, after a social media appeal by Survivors Manchester.