Yepp!

Jennifer Lawrence was on David Letterman and says:

"It's not my butt and I will not take responsibility for it" "It's a 90 year old butt that's been Photoshopped onto my body and is posing as my butt"

Must be hard being a celeb! lol.

You can catch her hosting SNL this Saturday ... and of course in the movie I CAN'T WAIT TO SEE ... "Silver Linings Playbook" with Bradley Cooper.

Anyways - here's the picture::