Cooper, a four-time Oscar nominee who's making his directorial debut with the film, stars as musician Jackson Maine. Cooper's Jackson discovers a struggling artist, Ally — played by Gaga in her first starring role — and the pair fall in love. The movie follows the couple's ups and downs set to a backdrop of country music.
Gaga — who was nominated for an Oscar for her 2015 song, "Til It Happens to You" — recorded original songs for the film, which she wrote with Cooper and a handful of artists, including Lukas Nelson, Jason Isbell and Mark Ronson.
The trailer gives fans their first look at the melancholy film, including singing from both Cooper, 43, and Gaga, 32. A Star Is Born also stars Andrew Dice Clay, Dave Chappelle and Sam Elliot and is set to hit theaters Oct. 5.