| Pelotas Basin | |
|---|---|
| Bacia de Pelotas, Cuenca de Pelotas | |
 The Lagoa dos Patos covers a large section of the onshore part of the basin | |
  Location of the basin in Brazil | |
| Coordinates | 32°06′40″S 48°55′50″W / 32.11111°S 48.93056°W |
| Etymology | Pelotas (a city in the state of Rio Grande do Sul) |
| Region | South Atlantic |
| Country |  Brazil Uruguay |
| State(s) | Santa Catarina, Rio Grande do Sul Cerro Largo, Rocha, Treinta y Tres |
| Cities | Porto Alegre, Rio Grande |
| Characteristics | |
| On/Offshore | Both, mostly offshore |
| Boundaries | Serras de Sudeste, Florianópolis High, Polônio High, Cuchilla Grande |
| Part of | Brazilian South Atlantic basins |
| Area | ~346,000 km2 (134,000 sq mi) |
| Hydrology | |
| Sea(s) | South Atlantic Ocean |
| River(s) | Urussanga, Araranguá, Mampituba, Jacuí, Guaíba, Camaquã, Jaguarão/Yaguarón, Cebollatí Rivers |
| Lake(s) | Lagoa dos Patos, Lagoon Mirim |
| Geology | |
| Basin type | Passive margin on rift basin |
| Plate | South American |
| Orogeny | Break-up of Gondwana |
| Age | Hauterivian-recent |
| Stratigraphy | Stratigraphy |
| Field(s) | none (2017) |
The Pelotas Basin (Portuguese: Bacia de Pelotas, Spanish: Cuenca de Pelotas) is a mostly offshore sedimentary basin of approximately 346,000 square kilometres (134,000 sq mi) in the South Atlantic, administratively part of the southern states Santa Catarina and Rio Grande do Sul of Brazil and the departments Cerro Largo, Rocha and Treinta y Tres of Uruguay.
The Pelotas Basin is one of the basins that formed on the present-day South Atlantic margins of South America and Africa due to the break-up of Gondwana in the Early Cretaceous. The sedimentary succession started as the other Brazilian marginal basins with a series of basalts, younger than the Paraná and Etendeka traps exposed in the Paraná Basin to the west, followed by shallow to deeper marine carbonate and clastic sediments. Other than the northern neighbours Santos and Campos Basins, the Pelotas Basin lacks a thick layer of salt and the pre-salt layer pinches out just in the north of the Pelotas Basin stratigraphy.
Within the Brazilian Atlantic margin, the Pelotas Basin is relatively underexplored. Twenty exploration wells have been drilled in the Brazilian portion of the basin with one ultra-deepwater exploration well drilled on the Uruguayan side in 2016. No hydrocarbon accumulations have been proven in the basin thus far.