Jennifer Lopez, Rihanna Pose Butt-to-Butt Backstage at iHeartRadio Music Awards: See the Sexy Picture!

Jennifer Lopez and Rihanna posed together backstage and compared their world-famous booties at the iHeartRadio Music Awards in L.A., Thursday, May 1. Credit: Larry Busacca/NBC/NBCU Photo Bank

Bumpin' booties! Jennifer Lopez and Rihanna compared their world-famous booties backstage at the iHeartRadio Music Awards in L.A., Thursday, May 1 -- and it was cheeky fun!

Together, the stars looked undeniably bootylicious, drawing attention to their enviable posteriors. J.Lo, 44, paraded around her unbelievably toned calves and bumpin' behind in a form-fitting sleeveless white minidress by Zuhair Murad.

Her sexy counterpart, 26, struck a more coy pose in her racy, sheer black gown that revealed her talked-about thighs and long legs.

J.Lo shared an Instagram pic of the two backstage early Friday morning and wrote, "congrats mama," to the Barbadian-born beauty.

While they have yet to collaborate on a track, RiRi and J.Lo have teamed up -- vocally-speaking -- on DreamWorks' upcoming animated movie, Home. Lopez will play the mother of Rihanna's teenage character Tip.

The animated comedy will be released November 26.