The That '70s Show co-stars had met during the Fox sitcom back in 1998 where they played love interests, but had started dating years later in 2012, and had gotten engaged in February 2014, People magazine reported.
The couple also welcomed their first child, daughter Wyatt Isabelle, in October.
Kunis, 31, had told W magazine that her first real kiss was with the 37-year-old actor and she was going to marry her "movie star crush."
If the reports are true, this is Kunis' first marriage, while Kutcher, who was previously married to Demi Moore, said "I do" for the second time.
Photograph: Justin K Aller/Getty Images
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