Cornell University is putting the brakes on fraternity parties for the rest of the school year ... and its president is admitting there's a serious drug and alcohol problem on campus.

In a letter to the campus community Tuesday, Cornell President Michael Kotlikoff announced all parties and social events inside Interfraternity Council houses are suspended for the remainder of the 2026-2027 academic year ... following explosive allegations surrounding an alleged 2024 gang rape.

And he's not messing around ... any fraternity caught hosting a party or social gathering inside its house will face immediate suspension.

Kotlikoff says the crackdown will give Cornell time to determine whether fraternity life can safely continue ... while acknowledging a "deeply disturbing prevalence of alcohol and drug abuse" that's not limited to Greek life.

The president also apologized for the harm Jane Doe allegedly suffered in 2024, saying he's "appalled" that sexual violence allegedly occurred within the Cornell community and admitting the university has fallen short.

The changes don't stop at frat parties ... Cornell plans to work with New York State Police to bring in independent investigators for sexual assault allegations, while adding more resources to support survivors.

As TMZ previously reported ... a woman identified as Jane Doe filed a lawsuit alleging she was drugged and gang raped by seven frat bros at a Cornell fraternity house in October 2024, sparking national outrage.

Former U.S. Deputy Attorney General Sally Yates is leading an independent review of Cornell's policies ... but Cornell's president says the university can't wait for those findings to take action.