Watch Madonna's amazing acoustic cover of Britney Spears' hit song Toxic

Madonna covered Britney Spears' song Toxic to mark the pop star's birthday.

The 59-year-old hitmaker paid tribute to her pal with a rendition of her famous track before wishing the singer a happy birthday on social media.

Captioning the video, Madonna wrote: "Silence =Death! ... Song For World AIDS Day! ... #toxic #poisonparadise @britneyspears. Happy Birthday!! (sic)"

Madonna and Britney teamed up for the track Me Against the Music for Britney's 2003 album In the Zone. That year, the pair also famously kissed on stage at the MTV Video Music Awards when Britney and Christina were duetting on Madonna's track Like a Virgin. The pop songstress then emerged out of a cake to sing her song Hollywood, before planting a kiss on Britney's lips.

Meanwhile, Britney is very happy with Sam Asghari, who she started dating after meeting him last year on the set of her Slumber Party music video, but had recently confessed that it was her who made the move first.

She shared: "We were waiting and waiting together for 20 minutes at a time, literally stuck there, [while filming the video]. We were forced to talk to each other.

"He doesn't really know me as a person, and I have no idea who the hell he is, and we were just talking. I kept his number, and it was so weird because it was like five months later that I found his number in my bag. I was like 'He was really cute. This guy was really cute!' so then I called him. He is just a really fun, funny person."

- Bang! Showbiz