The Avengers actress first met the comedian when she hosted Saturday Night Live in 2006, per Elle. The pair began dating in the summer of 2017. They went public in September of the same year, and Jost proposed in May, 2019.
On The Ellen Degeneres Show, Johansson said that Jost popped the question in a "James Bond" kind of way.
"He killed it. He's very charming and very thoughtful and romantic," she told the host.
Johansson, 35, has two previous marriages. She was with actor Ryan Reynolds from 2008 to 2011, and journalist Romain Dauriac from 2014 to 2017. She and Dauriac have a daughter named Rose.
Jost, who is one of the head writers for NBC's Saturday Night Live as well as a host on the show's Weekend Update, was previously involved with Parks & Recreation star Rashida Jones for three years. The pair broke up in 2016.
He previously admitted to SiriusXM that he was worried about being known as simply "Scarlett Johansson's boyfriend."
"I worried about my identity with it and also with comedy. I was always worried about anything that felt non-comedy, or took me out of a world of comedy," the 38-year-old confessed.
"You have to keep your own identity and do your own thing," Jost added.
The comedian mentioned his fiance in the acknowledgments for his memoir, A Very Punchable Face, this year, and wrote that he was considering having children.
In an interview in April, Johansson reflected on how her friendship with Jost evolved into a romantic relationship, as The Inquisitr reported.
"It's so funny to have a long-term shared experience with someone and then the relationship changes," she commented.
"What you see is what you get with him. He's very optimistic, easygoing, funny, nice, and those are the qualities that really drew me to him," the actress revealed.
Johansson also told fans that their main source of disagreement was baseball, since she's loyal to the New York Yankees and Jost is a fan of the Mets.
The pair initially delayed their wedding plans due to COVID-19.