The 34-year-old actress and the movie director have been married since 2003 and have a six-year-old son, Joe, together. London-based legal firm Schillings says the Oscar-winning actress separated from Sam, 44, earlier this year.
"Kate and Sam are saddened to announce that they separated earlier this year. The split is entirely amicable and is by mutual agreement. Both parties are fully committed to the future joint parenting of their children," lawyer Keith Schillings said in a statement this afternoon.
Kate and Sam married in May 2003 on the idyllic island of Anguilla in the Caribbean. Their son was born in New York where the pair spent most of their married life.
Kate was previously married to director Jim Threapleton, with who she has a nine-year-old daughter Mia Honey. She began dating Oscar-winning filmmaker Sam shortly after her divorce from Jim.