Her spokesperson confirmed the happy news, but did not disclose when it occurred or when they might tie the knot. "They haven't chosen a date for the wedding," she said.
The couple's engagement comes after a nine-month whirlwind romance.
A source says of the pair, "They're engaged and very happy."
Earlier this week, Scarlett was spotted wearing a beautiful vintage Art Deco style engagement ring at the 70th Annual Venice Film Festival.
The 28-year-old actress was there promoting her new sci-fi movie Under the Skin, in which she plays an alien seductress, and looked every inch the part as she sashayed up the red carpet.
She was as beautiful as ever in a figure-hugging off-the-shoulder black gown, as she beamed and showed off her new accessory.
Scarlett and her journalist fiancé may not have had time to take a romantic gondola ride, leaving Venice on Wednesday.
The couple began dating in November 2012 after being introduced by mutual friends, just weeks after Scarlett split from her boyfriend of one year, Nate Taylor.
"She broke up with him last week," a source told People magazine at the time. "He's pretty upset but the writing was on the wall. A lot of people were surprised it lasted this long."
The stunning actress was also married to Ryan Reynolds for two years, until the two parted ways in 2010.
Shortly after, Scarlett said that divorce is "like the loneliest thing you'll ever do, in some way."
Do you think Scarlett has found her love at last?