Live from New York, it's... an engagement!
Johansson, 34, and Jost, 36, have been dating for two years. The actress was previously married to actor Ryan Reynolds and to journalist Romain Cauriac, with whom she shares a daughter.
The marriage is the first for Jost, who co-hosts the hit NBC show's "Weekend Update" segment, and also serves as one of the show's co-head writers.
In 2017, Jost gushed about his now-fiancee to Entertainment Tonight, saying Johansson is "wonderful."
"She's pretty cool... It's hard to have a lot of complaints, she's pretty awesome," he said, adding that the first time the two met was when she hosted "SNL" in 2006 during his first year as a writer on the show.
The "Endgame" star's publicist told the AP that a wedding date has not yet been set.
The Associated Press contributed to this report.