(Photo by Andrew H. Walker/Getty Images for IMG)

Kate Upton celebrated her birthday by posting a TOPLESS image on Instagram!

Kate celebrated her 26th birthday by posting a boomerang of herself TOPLESS.  It's taken from behind, so you see major side-boob, but that's about it.

Put on my birthday suit to thank you for the birthday wishes! #wildone #26 #iknowyouwannaseemenakeynakeynaked

353 Likes, 5 Comments - Kate Upton (@kateupton) on Instagram: "Put on my birthday suit to thank you for the birthday wishes! #wildone #26..."