The "Avengers: Endgame" actress, 35, was first linked to the "Saturday Night Live" regular Colin Jost in May, 2017, when they were spotted kissing at an afterparty for the 42nd season finale of the hit comedy show.
And returning to the sketch show for her sixth stint as host, the star took a moment in her opening monologue to salute the show's co-head writer.
Explaining she felt she wasn't under much pressure in the role this time even if the show comes out bad, the "Marriage Story" actress joked, "What are they going to do? Fire my fiance?"
The 35-year-old, who is Hollywood's highest paid actress, went on to quip, "Oh no, what are we going to do without his paycheck?"
The couple got engaged in April and, speaking to U.S. talk show host Ellen DeGeneres, Scarlett confessed she was "surprised" by Colin's proposal.
"Even if you kind of imagine what that moment's gonna be like, it's still a beautiful moment... when someone tells you they want to spend their life with you, that's a lovely, special thing," she explained.