Reza's play, described as a satire, will begin previews at London's Gielgud Theatre March 7, 2008.
The run will precede the British actor's appearance at the National Theatre in a production of Oedipus, directed by Jonathan Kent, later in the year.
As with Reza's hit play Art, The God of Carnage will be directed by Matthew Warchus with a translation by Christopher Hampton. David Pugh and Daffyd Rogers will produce.
According to Rogers, God of Carnage is a comedy about parenting skills. The plot centers on two middle-class couples, who each have a nine-year-old son. Fiennes plays the lawyer father of a boy who attacks the other couple's son. All four parents get together to discuss what happened.
Reza's other credits include Life X 3 and Conversations After a Burial.
Fiennes, most recently on Broadway in The Faith Healer, is known to American audiences for his film roles in "Schindler's List," "The English Patient," "Red Dragon," "The End of the Affair" and "Quiz Show." The English actor has amassed a number of stage credits in his native country including Brand, A Midsummer Night's Dream, Romeo and Juliet, Six Characters in Search of an Author, Fathers and Sons, King John, The Man Who Came to Dinner, Playing with Trains, The Talking Cure and the Almeida Theatre Company’s production of Hamlet, which transferred to Broadway and earned him a Tony Award.