San Carlos () is a city in southeastern Nicaragua and the capital of Río San Juan Department. It is situated on the southern shore of Lake Nicaragua, at the confluence of the San Juan River. The municipality covers an area of and had an estimated population of 52,191 inhabitants in 2023. It serves as the administrative and commercial centre of the department.
History
The region was earlier inhabited by several Indigenous groups, including the Nicaraos, Pipiles, Caribs, and Miskito peoples. The Spanish conquistadors reached the San Juan River, known in early colonial references as El Desaguadero (the drain), in 1525. Some historians believe the site corresponds to the Spanish settlement of Nueva Jaén, reportedly founded by Captain Gabriel de Rojas in 1527. While the city served as a major center during the colonial era, its lost its importance later later. The municipality covers an area of . It serves as the principal administrative and commercial centre of the department.