A black Columbia University janitor is suing his employer, claiming the Ivy League institution is rife with racism.

In his Manhattan federal lawsuit, Oumar Coulibay, 36, of The Bronx, claims Columbia honchos not only give preference to white employees over promotions and bonus overtime — but also turn a blind eye while black workers are vilified with on-the-job racial slurs and tasteless pranks.

In the discrimination suit, filed Monday, he alleges the school and eight of its officials created a “hostile work environment” that triggered a litany of health problems for him since 2008 when he began working at a Columbia residential complex at 560 Riverside Drive.

“He’s been a longtime victim of racial and disability-based discrimination,” said his lawyer David DeToffol.

The suit claims the university barred black employees working in the residence from parking in its garage and other restricted parking spots, allegedly set aside for whites, and that a water cooler there once used by all staffers was relocated to a new location in which black staffers were denied access.

The suit also alleges many of Coulibay’s co-workers had a bias against President Obama.

For instance, a sign was hung in an employee kitchen area in 2008 with the slogan, “Don’t vote Muslim, Obama for President, Bernard for Vice-President,” and it included a photo of the White House “colored black.”

“Bernard” was another black porter at Columbia, the suit said.

Coulibay claims he’s been called many slurs by his co-workers, including “slave” and “voodoo man” and that his bosses not only ignored his repeated complaints — but threatened to suspend him for speaking up.

He has filed a complaint with the Equal Employment Opportunity Commission and is currently on leave because of his medical condition has “worsened” as a result the harassment, the suit says.

The suit list a laundry list of medical ailments for the janitor, including a heart condition.

He also claims he had to spent a month in a mental hospital and suffered headaches and chest pains because of stress suffered in a racist work environment.

He is seeking unspecified money damages.

Messages left with the university were not immediately returned.