The 35-year-old actress has been with her French actor boyfriend Guillaume Canet since 2007, after the pair met on the set of 2003 film Love Me If You Dare.
The happy couple have now announced via their representative that they are set to introduce their first child to the world. It has been reported the baby is due in the spring.
The news comes on the back of rumours suggesting that the couple were about to marry. Marion – who won an Oscar for her role in 2007 movie La Vie en Rose - was recently pictured wearing what seemed to be an engagement ring. However any plans for a wedding have been quelled by a source close to the couple.
"They haven't disclosed any plans concerning marriage," the source confirmed.
Marion enjoyed a successful career in 2010, appearing in box office hit Inception.