First Pics of Apollo Nida and His New Fiancee from Prison

Apollo Nida and his new chick celebrated their engagement by posing like a couple of kids at prom ... while he's doing hard time in a federal prison, and TMZ got the pics.

Nida slipped into his best prisoner khakis this past November during a visit from his gf-turned-fiancée -- and smiled for the camera in front of one of those backdrops you'd see at a photo studio. It's a service provided by the prison. Who knew?

As we reported, Apollo proposed to the mystery woman a few months ago. We're told 'RHOA' producers want to keep her name under wraps because she'll be part of the new season. She'll be on camera and he'll be on the phone, obviously.

One thing missing from the romantic shots -- an engagement ring.

Not to worry, we're told she went back for a visit last week, and this time she left with this non-sparkler, which appears to be a hair-tie/paper towel makeshift ring.

Imagine the insurance premium.