On the other hand, the name of Mesnil-le-Roi in the time of the French Revolution was Le Mesnil-Carrières, "Mesnil quarries".

Le Mesnil-le-Roi is situated between the Forest of Saint-Germain-en-Laye and the left bank of the River Seine.

The communal land includes an equal part of an island in the Seine, the Île de la Borde.

This autoroute crosses the Seine on a viaduct of reinforced concrete, forming two parallel bridges.

This coat of arms, adopted in 1952, derives from the La Salle family, the ancient landowners of Carrières-sous-Bois, and it was given to them by Francis I.