“This is going to be my first and only reaction to the whirlwind (of) news that broke 24 hours ago,” she said on Instagram late Wednesday.
“Many years ago, I met the man of my life, father of our son and of the baby we are expecting,” wrote the 40-year-old Cotillard, who has been with her partner Guillaume Canet since 2007.
“He is my love, my best friend, the only one that I need,” she said.
Soon after entertainment website TMZ reported Tuesday that Pitt and Jolie were divorcing, speculation arose of an affair between Pitt and Cotillard.
They are co-stars in the soon-to-be-released wartime thriller “Allied”, and filmed together in London.
Though Pitt and 41-year-old Jolie married two years ago, they have been a couple since 2004 and have six children together, three of whom are adopted.
Cotillard wrote: “I do very much wish that Angelina and Brad, both (of) whom I deeply respect, will find peace in this very tumultuous moment.”