| Official Name: | Mar del Tuyú |
| Pushpin Mapsize: | 200 |
| Pushpin Mapsize1: | 200 |
| Subdivision Type: | Country |
| Subdivision Type1: | Province |
| Subdivision Name1: | Buenos Aires |
| Subdivision Type2: | Partido |
| Subdivision Name2: | La Costa |
| Population Total: | 6,916 |
| Coordinates: | -36.5333°N -96°W |
| Elevation M: | 1 |
| Postal Code Type: | CPA Base |
| Postal Code: | B 7108 |
| Area Code: | +54 2246 |
Mar del Tuyú is a resort town and administrative seat of La Costa Partido, on the Argentine Atlantic Coast, with access to Provincial Route 11.
According to INDEC, the population of Mar del Tuyú was 6,916 in 2001, including (Costa del Este). It is included in a metropolitan area with Santa Teresita, raising the area's population to 19,950 inhabitants (INDEC, 2001).
The town was founded in 1945 by Arturo D'Elías. Upon the designation of the La Costa District in by the military-appointed Governor, Gen. Ibérico Saint Jean, in 1978, Mar del Tuyu was chosen as the county seat to avoid disputes between residents of the county's northernmost town, San Clemente del Tuyú, and the southernmost, Mar de Ajó (both of which are the largest in the district).