Rob Gronkowski's Ex a Finalist for S.I. Swimsuit Issue

Who's ready for chicks in bikinis?

We've got smokin' hot pics of 15 finalists all fighting for 1 spot in the S.I. Swimsuit issue ... including Camille Kostek -- the on-again, off-again GF of Rob Gronkowski.

Gronk's ex ain't the only hottie in the group -- its an All-Pro field with ladies of all shapes and sizes.

The contest started with thousands ... but S.I.'s only picking 1 to appear in the mag when the issue hits the presses.

How? We got no idea. But we're all winners here.