Sacha Baron Cohen & Isla Fisher Holy Moses ... It's A Boy!!

4/16/2015 4:00 PM PDT BY TMZ STAFF

 Sacha Baron Cohen Isla Fisher Baby Boy

Sacha Baron Cohen and Isla Fisher have made their first bouncing baby boy ... TMZ has learned.

We've obtained a copy of the birth certificate -- filed with the L.A. County Dept. of Public Health -- and it says Montgomery Moses Brian Baron Cohen was born on March 17.

It just came out last week they'd had the baby -- but they didn't say the name, sex or birth date.

MMBBC is the third child for Isla and the 'Borat' star. They have 2 daughters ... Olive, 7 and Elula, 4.

As for all the names, Isla's dad's name is Brian -- but we're at a loss on Montgomery and Moses ... outside of the 'Ten Commandments' guy.