Lady Gaga announces Bruno Mars duet, 'Die with a Smile'

After several hints -- including posts of them wearing each others' T-shirts -- Lady Gaga and Bruno Mars have officially confirmed they're releasing a duet.

Gaga posted a photo to Instagram Thursday of herself and Mars wearing coordinating blue and red retro-style country-western outfits, along with the title of the song: "Die with a Smile."

The "Born This Way" singer made it clear in her caption that this single is not part of her eagerly anticipated next album.

"WHILE YOU WAIT TILL LG7…'DIE WITH A SMILE' a duet with @brunomars," she wrote in the caption. "Song and video tonight at 9pm PT."

Speculation is that the song was recorded for Gaga's upcoming movie with Joaquin Phoenix, "Joker: Folie à Deux." The Todd Phillips-directed film will premiere at the Venice Film Festival on Sept. 4.