The "Luther" star proposed to model Sabrina Dhowre on Saturday at Rio Cinema in London where he was screening his directorial debut, "Yardie."
In one fan video, Elba, 45, is seen down on his knee before popping up to hug his now fiancee. The two then hug as the audience applauds loudly.
ABC News reached out to a rep for Elba, but didn't immediately hear back.
The news of his engagement comes months after the actor was quoted as saying he'd never get married again.
"Am I ever gonna get remarried? I don't think so. Yeah, I don't think so," he told Essence magazine last July. "Marriage is an institution of sorts. And I've done it. It's not for everybody. It's not my life's calling."
"Falling in love while making a movie about falling in love is pretty special," Elba said last year.
This will be the third marriage for Elba, who was previously wed to makeup artist Hanne Norgaard and lawyer Sonya Hamlin. Elba and Norgaard are parents to a 15-year-old daughter named Isan. He's also a father to Winston, born in 2014, with makeup artist Naiyana Garth.