The song arrives through Darkroom/Interscope Records and will be featured on HBO's upcoming second instalment of the Euphoria pandemic episodes.
The song's early iterations began a few years, Eilish explained in a recent interview with Zane Lowe: "It went through lots of stages, which is kind of rare for us. Usually, the production we do is the production we end up with. And this one was really not that way. And obviously, it was like, two years, so obviously it's gonna change."
She added that the final product "just works" and called it "so weird."
Last year, Rosalía teased the collaboration in an interview with Apple Radio.
"During these two last weeks I have been trying to finish the Billie Eilish collab," she said at the time. "I think it's getting quite closer. I think that the arrangements, I think that yesterday I finished the arrangements. I feel like the production, the sound design, is almost done, so I just need that Billie maybe sends the vocals and they send me the ideas that they want to add because we are there."
Watch the video below.
Listen to Billie and @Rosalia's "Lo Vas A Olvidar" on @applemusic. https://t.co/p2yxBIYvRW— billie eilish (@billieeilish) January 21, 2021
Listen to Billie's interview with @zanelowe coming soon on Apple Music 1. https://t.co/DWU86DgBkE pic.twitter.com/DcglaPzFkr
"I don't feel like I've heard a song that sounds like this."@billieeilish and @zanelowe talk #LoVasAOlvidar, her new collaboration with @rosalia.— Apple Music (@AppleMusic) January 21, 2021
Catch their chat now on Apple Music 1: https://t.co/i1NRuixsJW pic.twitter.com/fSfiD3xlqZ