He surrendered before police around 10.15 p.m. at Vasant Kunj north police station in south Delhi, a senior police officer said.
Ratan had allegedly raped the girl a few days back after luring her to his hostel room on the pretext of giving her the copy of a movie she wanted and then giving her a drink spiked with a sedative.
An activist of the All India Student Association (AISA), Ratan was expelled from leftist student outfit after the allegations against him.