Saint-Ouen-sur-Seine is a commune in the Seine-Saint-Denis department in the Île-de-France region of France. It is located in the northern suburbs of Paris, 6.6 kilometres from the centre of Paris. The commune was officially called Saint-Ouen until 2018, when its name was changed by ministerial order.
The communes neighbouring Saint-Ouen-sur-Seine are Paris, to the south, Clichy, to the west, Villeneuve-la-Garenne, Gennevilliers and L'Île-Saint-Denis, to the north, and Saint-Denis to the east. The commune of Saint-Ouen-sur-Seine is part of the canton of Saint-Ouen, which also includes L'Île-Saint-Denis and part of Épinay-sur-Seine. Saint-Ouen also includes the Cimetière de Saint-Ouen.