Ustaritz (French pronunciation: [ystaʁits]; Basque: Uztaritze) is a town in the traditional Basque province of Labourd, now a commune in the Pyrénées-Atlantiques department, southwestern France. It is located on the river Nive some 13 kilometres (8.1 mi) inland from Bayonne. Ustaritz station has rail connections to Saint-Jean-Pied-de-Port, Cambo-les-Bains and Bayonne.

Ustaritz was the location of the assembly of local Basque leaders before the French Revolution.^{[citation needed]} The 19th-century French playwright and historian Jean-Joseph Ader (1796–1859) was born in Ustaritz.