Saint-Quentin-en-Yvelines is a new town and an agglomeration community located in the French department of Yvelines. Situated approximately 25 km (16 mi) west of the center of Paris, it is an integral part of the larger Paris metropolitan area.
The town was developed from a greenfield site beginning in the 1960s and is recognized as one of the original five villes nouvelles of Paris. It covers an area of 119.2 km2 and was named after the Saint Quentin Pond, which serves as the town's center. As of 2018, the population of Saint-Quentin-en-Yvelines was 228,312.