Luigi Mangione and Diddy Being Held in Separate Units at New York Jail

Luigi Mangione is not hanging out with Diddy at one of America's most notorious jails ... because they're being held in totally different cell blocks.

Sources with direct knowledge tell TMZ ... Luigi and Diddy are not in the same jail unit at MDC Brooklyn.

Reports surfaced last week speculating Luigi and Diddy would soon be held in the same protective jail unit, but we've learned that's not the case.

In fact, our sources say Luigi and Diddy have had not contact with each other at all since Luigi was brought in.

Luigi was booked into MDC Brooklyn last week after being extradited from Pennsylvania to NYC to face murder charges in the slaying of UnitedHealthcare CEO Brian Thompson.

Diddy's been locked up at the same jail since his September arrest ... as he awaits trial in his sex trafficking case.

The Federal Bureau of Prisons tells TMZ ... "For privacy, safety, and security reasons, we do not discuss internal security procedures or the conditions of confinement for any individual, including housing assignments."

We reached out to Luigi's reps, who declined to comment.