| Ustaritz | |
| Native Name: | Uztaritze |
| Commune Status: | Commune |
| Arrondissement: | Bayonne |
| Canton: | Ustaritz-Vallées de Nive et Nivelle |
| Insee: | 64547 |
| Postal Code: | 64480 |
| Mayor: | Bruno Carrere[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | CA Pays Basque |
| Coordinates: | 43.4003°N -1.4553°W |
| Elevation M: | 9 |
| Elevation Min M: | 0 |
| Elevation Max M: | 143 |
| Area Km2: | 32.75 |
Ustaritz (in French pronounced as /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 13km (08miles) 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. The 19th-century French playwright and historian Jean-Joseph Ader (1796–1859) was born in Ustaritz.