According to People magazine, the couple got married in a private ceremony over the Fourth of July weekend.
News of the wedding may come as a surprise as it has been speculated for some time that the couple actually married some time ago.
In January, the Two and a Half Men star posted a message on his Facebook page which featured the words ‘Happy New Year Love The Kutchers’ drawn in the sand, fuelling speculation they had wed in secret.
Ashton, 37, and Mila, 31, met while playing love interests on That ’70s Show, which ran from 1998 to 2006, However, it was not until 2012 that they began dating.
They welcomed baby daughter Wyatt Isabelle in October after getting in engaged in February 2014.
Last year, the Black Swan actress told W magazine: “We all get movie star crushes. I’m marrying mine.”
Ashton’s divorce from Demi Moore was finalised in November 2013, while Mila split from Macaulay Culkin in 2011 after an eight-year relationship.
Earlier this year, there was speculation that the pair had already secretly wed, after Mila cryptically responded to chat show host James Corden’s question: “Have you gotten married?” with: “I don’t know. Maybe.” Kunis has admitted that she has always had a soft spot for her co-star.
“My first real kiss ever was with him on the show,” Kunis said in W magazine’s August issue.
A source told New York Post gossip column Page Six guests were only informed of the wedding details 24 hours or less beforehand.
“It was a very small and intimate affair with friends and family,” said the source.