Billie Eilish and Rosalía Team up for 'Beautiful,' Haunting Spanish Duet 'Lo Vas a Olvidar'

Billie Eilish and Rosalía have finally dropped their long-awaited collaboration.

Nearly two years after they were first spotted in the studio together, the two singers released a new Spanish-English duet titled "'Lo Vas a Olvidar" ("You Will Forget Her" in English) on Thursday, along with its accompanying dreamlike music video.

Produced by Eilish's older brother and frequent collaborator, Finneas, the track will appear on an upcoming special episode of HBO's Euphoria titled "Part 2: Jules," airing on Sunday at 9 p.m. EST.

During an interview with Apple Music's Zane Lowe on Thursday, Eilish, 19, gushed about the song, saying she "loved" it when she heard it finished.

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Matty Vogel & Zhamak Fullad Billie Eilish and Rosalía

"It went through lots of stages, which is kind of rare for us," she said. "Usually the production we do is the production we end up with. This one was really not that way. Obviously, it was like two years, so obviously you're going to change."

"It just worked," she added. "The time I heard it when it was done, I was like, 'This is so weird.' I don't feel like I've heard a song that sounds like this, but I do feel like it's weird and different."

Though Eilish previously covered Carla Morrison's "Eres Tú" during an Instagram live in 2017, the song marks the first time she has released an original in Spanish.

"Obviously, a lot of it is in Spanish, which I think is so important," Eilish told Lowe. "I remember when we were writing the song, [Rosalía] saying something about [how] it should be in English. I was like, 'No, no, no. It should be in Spanish. It's so beautiful.'"

Rosalía — who's from Barcelona, Spain — first got fans excited about the duet back in March 2019, when she shared a photo of her and Eilish to Twitter, writing, "Can't wait to finish our song."

Can’t wait to finish our song 🖤 compartir contigo en el estudio o verte ayer actuar me inspira sooo much, love you B pic.twitter.com/TxV3J7D1QQ

— R O S A L Í A (@rosalia) March 10, 2019

"Being with you in the studio and seeing you yesterday inspired me sooo much," the 27-year-old added in Spanish. "Love you B."

Rosalía, then spoke about the collaboration during an interview with Billboard last April, saying she was "trying to finish" it.

"I think it's getting quite close," she said. "Yesterday I finished the arrangements. I feel like the production, the sound design is almost done, so I just need Billie to send the vocals and they send me the ideas that they want to add because we are there."

Amy Sussman/Getty; Europa Press via Getty Billie Eilish; Rosalía

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The duet is just the beginning of what's still to come this year for Eilish, who is up for four awards — including song and record of the year — at the 2021 Grammys airing March 14. Next month, she'll also premiere her new AppleTV+ documentary, Billie Eilish: The World's A Little Blurry.

Rosalía, meanwhile, has been hard at work over the last year immersed in the creative process of writing and recording her eagerly-awaited, yet-to-be-titled third studio album.