4:11 PM PT -- A source close to Cardi tells us the baby in the video isn't Kulture, in fact, it's not a real baby at all.

Cardi B took "bring your daughter to work day" to a whole new level ... by featuring Kulture in a not so traditional way in her brand new music video.

The rapper goes topless in her vid for "Money" -- which dropped Friday -- to breastfeed her baby girl, Kulture. Because it's Cardi, there's also no shortage of her in lavish outfits, sexy dance moves ... and shots of her ass.

Who knew she played piano?

As we've reported ... Cardi's been pretty stingy providing pics or vids of her daughter, but made a big reveal shortly after announcing her split with Offset.

Offset announced on his birthday he wanted Cardi back, and to spend Christmas together as a family. He also crashed her stage at Rolling Loud last weekend with $15,000 in roses ... only to be rejected in front of a ton of people.

Kulture was hidden from the world for a long time ... but she's definitely getting tons of attention now though.

Originally Published -- 12:08 PM PST