According to the site's source, the two wed in New York City on Friday evening during a small ceremony. Olsen, 29, and Sarkozy, 46, had been dating for three years and engaged since February.
Interestingly, the event's decor was described as involving "bowls and bowls filled with cigarettes," while cocktails were held in a back garden prior to an indoor dinner and ceremony.
Olivier is the half-brother of former French president Nicolas Sarkozy. It was his second marriage, the first having ended in 2011, and Olsen's first.
No word yet on who was in attendance, but we imagine Mary-Kate's twin, Ashley, was there.
After all, It Takes Two.