Luigi Mangione's Bleak Birthday Meal Behind Bars Revealed

The feds would probably say Luigi Mangione got his just desserts on his birthday -- 'cause he had to nosh on some crappy prison food!!!

TMZ obtained a copy of Luigi's breakfast, lunch and dinner menus for his 27th birthday Tuesday, while locked up at the Metropolitan Detention Center in Brooklyn, New York.

And while much of the food is the type of stuff we all eat ...it all seems kind of nasty when you factor in the whole jailhouse aspect.

For breakfast, Luigi had a choice of fruit, cereal, breakfast cake, sugar substitute packets and skim milk. Don't confuse breakfast cake with birthday cake. It certainly wasn't the latter.

Then for lunch, the feds went all Italian on Luigi, offering him pasta with meat sauce and chickpea marinara, as well as spinach, whole wheat bread, fruit and a beverage.

Dinner seemed pretty grody ... at least on paper. Luigi was served a chicken patty sandwich or chickpea burger (eww!), steamed rice, pinto beans, lettuce, tomato, mayonnaise, hamburger bun and a beverage.

Not exactly Wolfgang Puck, like we said. But since Mangione is criminally charged with fatally shooting UnitedHealthcare CEO Brian Thompson in Manhattan in December, the feds don't seem to mind.

Federal prosecutors later added charges charged Luigi in an indictment with stalking and murder -- and U.S. Attorney General Pam Bondi has said she will seek the death penalty. New York state prosecutors have also charged Luigi with multiple counts of murder and criminal possession of a weapon.