Britney Spears -- Sorry, Madonna ... I Kiss Iggy Azalea Now!

Iggy Azalea and Britney "Tan Mom 2.0" Spears nearly shared a liplock on the set of their new music video Thursday in Malibu.

They wigged out and wore their best white trash outfits -- possibly their own.

It's a little "circle of life"-ish if you think about it ... it wasn't that long ago Britney was the young hot chick kissing the old music vet in a desperate attention grab ... and now the stiletto is on the other foot.

Man, time sure flies, huh?