Police say the woman, who is in her early 20s, was subjected to a “serious sexual attack”.
The brutal attack happened around 3.30 am in Rosemary Street.
The victim had been waiting for a friend to collect her when the attack happened.
Her friend gave chase to the attacker when he arrived.
But the man escaped and fled in the direction of Royal Avenue.
Police are currently studying CCTV footage from cameras dotted Rosemary Street and Royal Avenue to try and identify the attackers.
The PSNI have appealed for anyone with information to contact them on the 101 non-emergency number.