Amber Rose & 21 Savage Make It Rain

Amber Rose and 21 Savage took a trip to his hood and quickly turned a club appearance into the ultimate ladies night out ... by dropping $22k just for the ladies.

The new couple popped in at Club Crucial in Atlanta Monday night, where Savage was promoting his new record, "Issa Album" -- while onstage, they started hurling cash into the crowd. 

We're told it's actually a ritual every Monday night -- giving back to the community, especially women. Amber and Sav seemed more than happy to carry on the tradition.

As we reported ... Amber and Savage are in a full-blown relationship ... they've even met each other's families.

Like they say -- the couples that make it rain together, slay together. Nothin' new there.