Lady Gaga and Bradley Cooper Make Out on Set of 'A Star is Born'

Lady Gaga and Bradley Cooper shared a passionate and long kiss at a gas station ... for a movie, of course.

Gaga's making her big screen acting debut in the remake of "A Star is Born." She'll be playing alongside Cooper, who's also making his directorial debut.

The duo shot a sexy scene Monday in the California desert, where they will also film scenes on the Coachella grounds during the week ... which is super convenient for Lady Gaga, who headlines again this coming weekend.