A new DC star is born.

Lady Gaga is in early negotiations to join “Joker: Folie à Deux” as Joker’s partner-in-madness, Harley Quinn, for what would be a musical sequel to director Todd Phillips’ 2019 blockbuster.

Speculation that Harley Quinn would appear in the movie first bubbled to the surface after Phillips posted the cover of the screenplay to Instagram on June 7. The subtitle, Folie à Deux, refers to a shared delusional disorder, and Joker’s only real companion — other than Batman, anyway — has been Quinn, a character first created for “Batman: The Animated Series” in the early 1990s.

Making “Joker 2” a musical is another bold stroke by Phillips, who struck gold — at the box office (with $1 billion in worldwide grosses) and the Oscars (with 12 nominations and two wins) — when he reframed the Dark Knight’s number one villain as a loner anti-hero. Joaquin Phoenix won best actor for his performance as Joker, aka Arthur Fleck; he’s also expected to reprise his performance, though his deal isn’t settled yet.

All other details about “Folie à Deux” remain under wraps, so it’s unclear whether Gaga would also contribute any music to the project, but it’s a safe bet that it’s at least on the table. Gaga worked with Phillips in his capacity as one of the producers of 2018’s “A Star Is Born,” which earned Gaga an Oscar nomination for best actress — and an Oscar win for original song. That movie’s star and director, Bradley Cooper, was also a producer on “Joker,” but it’s unclear what level of involvement he has on “Folie à Deux.”

Harley Quinn has proven to be a durable character for Warner Bros. Margot Robbie has played the role three times, in 2016’s “Suicide Squad,” 2020’s “Birds of Prey” and 2021’s “The Suicide Squad,” and Kaley Cuoco voices the character on the popular HBO Max animated series “Harley Quinn,” which is set to premiere Season 3 later this year. Phillips’ “Joker” movies, however, occupy a separate storytelling universe from the rest of DC’s output, similar to how Robert Pattinson’s “The Batman” can exist alongside Michael Keaton’s version of the character, who will appear in 2023’s “The Flash.”

The Hollywood Reporter first reported the news about Gaga.