Herblay-sur-Seine (French pronunciation: [ɛʁblɛ syʁ sɛn], lit.

"Herblay-on-Seine"; before 2018: Herblay)[3] is a commune in the Val-d'Oise department in the Île-de-France region in Northern France.

It is located 20.2 km (12.6 mi) from the centre of Paris, in its northwestern outer suburbs, on the departmental border with Yvelines.

The average annual rainfall is 612.5 mm (24.11 in) with October as the wettest month.

Herblay-sur-Seine is served by Herblay station on the Transilien Paris-Saint-Lazare suburban rail line.