Forêt de Marly, Royal forest in Yvelines, France.

Forêt de Marly is a 2,000-hectare forest estate in the Yvelines, about 20 km west of Paris between Saint-Germain-en-Laye and Versailles. It runs roughly 12 km east to west across eleven communes, from Louveciennes and Marly-le-Roi to Saint-Nom-la-Bretèche and Feucherolles. The canopy is a continuous mass of broadleaf green, with slender trees with umbrella-like crowns rising above it in places. The A13 motorway cuts through its whole length.

The forest was called forêt de Cruye until the 18th century, when Louis XIV acquired the seigneurie de Marly by exchange to build his château de Marly around 1690. Around 1215, Barthélemy de Roye built a castle here after the Battle of Bouvines, now the ruined château de Retz. Presidential hunting ended in 1995 under Jacques Chirac, replaced by administrative regulation hunts.

The forest's old name, forêt de Cruye, survives in the hamlet of Noisy-en-Cruye, recorded in 1369, and in Bailly-en-Cruye, recorded in 1463. The name Marly replaced it around 1690, when Louis XIV acquired the seigneurie de Marly to build his château there. The forest is now a domaine of the Office national des forêts, and since 1995 presidential hunting has been replaced by administrative culls to regulate game.

The forest has no gate or opening hours; it is a domanial forest crossed by the A13 motorway, which splits it along its whole length and is fully fenced, blocking wildlife movement. The A13 crosses east-west, while the D7, D161 and D98 run north-south through the middle; the D186 marks the eastern edge and the D30 the western edge. The Rocquencourt interchange, where the A12 meets the A13, lies inside the forest.

The A13, France's first motorway, opened on 9 June 1946 and runs the length of the forest, fenced off and blocking animal movement. The Plaine de la Jonction, bought by the state under the Second Empire to link the two hunting estates, now lets wild boar from Marly repopulate the forêt de Saint-Germain-en-Laye.