The shocking incident happened in Bochum, a city in the western German state of North Rhine-Westphalia.
According the student's account, she was grabbed on a bridge and pushed into some nearby bushes, where she was attacked.
She said: "He did not understand German nor English, was obviously not a student, had a beard and looked like he came from the Middle East."
The local police have made a composite drawing of the suspect, and have started a manhunt.
It was not the first sex attack in Bochum on a female student in the area, as already in August a 21-year-old was sexually assaulted by an "Arab or Afghan looking man" according to a police report.
The fear among some women on university campuses is high, as the incident came days after 19-year-old student Maria L. was sexually assaulted and murdered in the southern city of Freiburg by an unknown perpetrator.
She advises all women to avoid encounters with foreign, individual men during the day, as the report says. She had been frightened she would be murdered by the sex offender just like Maria L: "When it happened, I reacted so calmly and reasonably that I was astonished by myself."
She could not scream for help, as the perpetrator choked her with force, the victim added.