Celebrity Butts

Kylie Jenner may be the birthday girl, but Tyga's the one who scored the best gift.

Kylie backed that big ol' butt up right into her BF's crotch during a beach outing in Turks and Caicos.

The Summer Olympics in Rio are less than a week away, but the hottest contest down there is Miss Bumbum 2016 -- and all signs point to a stiff competition.

Khloe Kardashian literally ripped her pants off piece by piece ... or so it seemed.

Some things change, but a Kardashian will always deliver from behind.

Here's Serena Williams getting a sports massage in a one-piece bathing suit and we assure you it's EXACTLY what you need to get through the rest of your work day.

The short vid went up on SW's Snapchat moments ago ... and while it doesn't quite live up to the bootyful star-spangled outfit she wore on Snap some months back -- we assure you of one thing:

You won't be disappointed.

So watch ... and check out Serena's devilish grin. She knows what she's doing.

Lady Gaga looked surprisingly comfortable with a solid and snug wedgie as she lounged poolside in Cabo.

Here's Rihanna performing in Glasgow ... on a glass catwalk.

Keep in mind, SHE posted this video -- so she's clearly proud of her work. And why wouldn't she be?

The Olympics aren't until the summer but Lolo Jones is competing early ... in the booty games.

Jones posted a pool pic to Instagram with some of her training partners ... giving us a view of what (some) of her opponents see when they race her ... her All-American backside.

We say gold medal ... but be your own IOC judge ... bronze, silver, or did she trip on the hurdle yet again?

Here's celebrity twerk instructor Lexy Panterra throwing out the first pitch at a Miami Marlins game moments ago ... and twerking while she does it of course.

Lexy's a big deal who's taught the art of the twerk to celebrities like Mel B, Christina Millian, and Tiny so it makes sense the Marlins would have her toss one out.

Look ... we're not gonna get too deep here ... her pitch was fine (better than 50 Cent) but this is all about the little wiggle she gives before the throw, and the big wiggle in her video below.

Enjoy.

Blake Lively has pissed off the black community in a big way ... by captioning this pic that she now has an "Oakland booty."

Blake, who's pregnant with her second kid, is in Cannes and pretty clearly was just joking with the Instagram post, but it's inflamed lots of people on social media.

Blake was clearly gabbing a line from Sir Mix-a-Lot's song, "Baby Got Back (I Like Big Butts)."

Some of the people who are throwing shade think Blake is using black women as a punchline.

Notably, this doesn't seem to be simply a black/white thing. Katy Perry and Khloe Kardashian have used the quote on social media ... without getting ripped.

Uh-oh Shakira ... the hottest ass in the universe might be trying to score with your baby daddy ... 'cause Miss BumBum is putting her two best cheeks forward to get the attention of soccer superstar Pique.

Suzy Cortez -- the reigning Miss BumBum (basically the best butt in Brazil) -- has been targeting Pique on the 'Gram ... posting sexy pictures wearing his jersey ... and tagging Pique in the photos.

It wasn't exactly sliding into Pique's DMs, butt it signals she's a huge fan ... and fans have been known to do wild things for the players they love ... aka have sex with them.

BTW -- it's not Suzy's first time on the pitch ... she was reportedly blocked on IG by Lionel Messi and his GF for sending the Argentine footballer some sexy shots a while ago.

Get that block button ready, Shakira.

Khloe Kardashian's still got a lot of junk in her trunk despite a rigorous workout regime that has every other part of her body slimming down.

Khloe ran errands Monday in Bev Hills, hitting up the Meche hair salon -- but in boots and jeans like this ... NO one was paying attention to her hair.

Ass ... still that family's greatest export.

Bella and Gigi Hadid clearly are cut from the same cloth ... from behind they are mirror images.

The models -- strolling side by side through NYC -- are two years apart, but from behind they tell the same tale.

Happy Friday ... if you're Jessica Alba, who gets to spend it in Hawaii (again) in a bikini that's quickly being devoured by her incredible ass.

Bella Thorne hit South Beach in a bikini that fought a losing battle ... against her ass.

Heidi Klum's BF is a serious brown-noser -- and a lucky son of a bitch.

Klum and Vito Schnabel got very playful Thursday in St. Barts, where he was happily -- we're sure -- behind her efforts to get up on a surfboard.

Check out the pics ... Vito caught a few waves, but Heidi was satisfied sunning her buns on the board ... which seemed just peachy to him.