"Because it's the last night on Earth, Ellie is a big fan of Planet Earth by David Attenborough, so I would and watch that with her. For that reason, Ellie Goulding," the star told host James Corden.
Horan dated Goulding in 2013 and was linked to Gomez in late 2015. He also chose Goulding over Diane Keaton, Rita Ora, Jennifer Lopez and Kendall Jenner while playing "Who'd You Rather" on Thursday's episode of The Ellen DeGeneres Show.
"Good news everyone, I found a girlfriend for @NiallOfficial. I hope you're watching, @EllieGoulding," DeGeneres tweeted after the show.
"We're still friends," she revealed. "We went on a few dates, and it was really fun. He's a really, really lovely guy. He's got the biggest sense of humor, he's very caring, and I see him as a genuine friend in the industry."
Horan is best known as a member of the British boy band One Direction, which is presently on an indefinite hiatus. The singer released his first solo single, "This Town," in September after landing an album deal with Capitol Records.