Serena Williams is an athlete that always seems laser-focused whenever she's mid-match (and it pays off, judging by her ample wins). So, when we catch her off the court, we like seeing the tennis pro shake it out. In her latest campaign, Williams is dancing with herself, in more ways than one. And, of course, we can't get enough of it. The newly-engaged tennis champion's latest spot for Australian intimates brand Berlei is too much fun. Williams has been an ambassador for the brand for several years now, but her campaign for the brand's newest sports bra is just too much fun. In the video below, we see Williams let loose as she freestyles along to The Donnas' cover of Billy Idol's famous "Dancing With Myself" jam. Who knew she was such a fan of one of our favorite songs to dance to when no one's watching?