The movie beauty plays a paraplegic orca trainer in the acclaimed Jacques Audiard film, which received rave reviews when it premiered at the prestigious festival in the South of France.
Cotillard was widely tipped to take home the Best Actress prize at Cannes and industry experts were shocked when the jury awarded the honour jointly to Romanian stars Cosmina Stratan and Cristina Flutur for their performance in Beyond the Hills.
The Oscar winner believes her global success following her star turn in Edith Piaf biopic La Vie En Rose was partly to blame for the oversight.
She tells W magazine, “I think I may have been on too many magazine covers. In France, they like the underdog. In America, they appreciate success.”