The Black Widow actress sparked rumours of a pregnancy back in July when "multiple sources" confirmed the news with Page Six.
"Scarlett is actually due soon, I know she and Colin are thrilled," a source told the publication at the time.
Another said: "Scarlett is pregnant but has been keeping it very quiet. She has been keeping a very low profile."
This will be the first child for Jost, who is a stand-up comedian, actor and writer.
Johansson also has a six-year-old daughter, Rose, to her former husband Romain Dauriac.
Scarlett and Colin married in October 2020, but kept the occasion very private—as has been the case for much of their romance.
Her due date is unknown, though it may not be too far away given reports last week the actress has signed onto a new Wes Anderson film, also set to star Margot Robbie, Tom Hanks and Tilda Swinton.
Watch this space, joyful updates await.