Regina Hall Drops Hilarious Birthday Song to Celebrate Turning 50

Regina Hall turned 50 this weekend, but she has NOT lost her sense of humor ... if anything, it's sharper -- and she's leaning into it with an awesome song for her big day.

The actress and comedian rang in the big 5-0 Saturday with a hilarious home video and song she wrote -- in which she gives praise for reaching a life milestone ... and still looking great while doing it -- something RH is well aware of, as you can see.

Regina says her motive for the ditty's pretty simple -- "Because laughter keeps you forever young I wrote a special song for a special Birthday."

The song has the same refrain/hook throughout -- "A bitch is old today," which is sung a cappella style and carried on beat with claps in the background. It looks like Regina had a little help making this, and she shouted out all the cameos on and behind the camera.

Anyway, back to the song. It gets pretty raunchy -- right up Regina's alley -- because at one point she talks about being 50, but also still having good ... uh, well, all the parts still work. And then some.

The video shows you around her home, including her pool and trampoline -- where she bounces around for fun. She's also seen hanging out with some younger gals in bathing suits, who help hit a certain line home about shouting out young "bitches" ... and old ones.