Monthyon (French pronunciation: [mɔ̃tjɔ̃] ⓘ) is a commune in the Seine-et-Marne department of the Île-de-France region in north-central France.

The Belgian painter Eugène Boch lived in the Villa La Grimpette.

[3] In 1959, French actor Jean-Claude Brialy acquired a château in the commune; he lived there, with his partner, until he died in 2007.

[4] From a population of 858 in 1975,[5] Monthyon grew to 1,730 by 2018.

[5] The inhabitants of Monthyon are called Monthyonnais.