Jon Hamm and Becky G Dance Their Buns Off at Bad Bunny Concert

Bad Bunny's weekend concert in Puerto Rico drew a bunch of A-listers -- among them Jon Hamm and Becky G -- who danced their buns off during the show!

Jon and Becky got into a dance-off of sorts ... with Hamm hamming it up in a bucket hat and Hawaiian-style getup, while Becky sported a red bra with matching thong.

The "Mad Men" actor was striking poses with his posse as Becky -- ever the singer -- mouthed the words to one of Bunny's songs and sashayed her hips.

It's no secret ... Bunny's been getting his audiences into the groove routinely over the past month as part of his first music residency, “No Me Quiero Ir de Aquí." And it's all going down at José Miguel Agrelot Coliseum in San Juan, Puerto Rico, the territory where he was born and bred.

At many of his shows, Bunny has hit the stage in front of a slew of celebs, including LeBron James, Ricky Martin and Austin Butler.

And let's not forget Jon and Becky. The question is, who showed off the better moves? Weigh in!