Serra do Mar (Portuguese: Mountain Range of the Sea) is a 1,500 km long system of mountain ranges and escarpments in Southeastern Brazil, which runs in parallel to the Atlantic Ocean coast from the state of Espírito Santo to southern Santa Catarina, although some include Serra Geral in the Serra do Mar, in which case this range extends to northeastern Rio Grande do Sul. The main escarpment forms the boundary between the sea-level littoral and the inland plateau (planalto), which has a mean altitude of 500 to 1,300 metres (1,600 to 4,300 ft).
The mountain ranges are discontinuous in several places and receive individual names such as Serra de Bocaina, Serra de Paranapiacaba, Serra Negra, Serra do Indaiá, etc. It also extends to some large islands near the coastline, such as Ilhabela and Ilha Anchieta. With an altitude of 2,255 metres (7,398 ft), Pico da Caledônia in Nova Friburgo and Cachoeiras de Macacu in Rio de Janeiro is among the higherst points in Serra do Mar.
Geologically, the range belongs to the massive crystalline rock platform that forms Eastern South America and tectonically is very stable. Most of the elevations of Serra do Mar were formed about 60 million years ago.
At the time of discovery of Brazil (1500), Serra do Mar supported a rich and highly diversified ecosystem, composed mainly by a lush tropical rain forest, called Atlantic Forest (Mata Atlântica). Due to urbanization and deforestation, however, most of the forest cover was destroyed and it remains almost exclusively in the steep escarpments facing the sea. A chain of national and state parks, ecological stations and biological reserves now protect the Mata Atlântica and its biological heritage, but acid rain, pollution, poachers, clandestine loggers, forest fires and encroachment by urban areas and farms are still promoting active destruction, particularly around cities. Several large metropolises are near the Serra do Mar, including São Paulo and Curitiba.
Reforestation and recuperation of biological diversity are notoriously difficult to bring about in destroyed rain forest habitats.