Maresias, Beach and district in São Sebastião, Brazil.

Maresias is a beach and district of São Sebastião on São Paulo's northern coast, its yellowish sand running about five kilometres along the Atlantic. The sea carries big waves and a strong current, and the sand meets Atlantic Forest slopes behind the shore. The district counted 31,184 inhabitants in the 2010 census.

Surfers reached the beach in 1974 while searching for new waves north of Guarujá. The discovery led to a permanent community forming over the following decades.

The name Maresias comes from the ocean breeze that hits the beach and the neighbourhood. The beach hosts national and international surf championships, drawing competitors from across Brazil and South America, and it is where the surfer Gabriel Medina was born in 1993.

Roads from São Sebastião lead directly to the beach, connecting it to larger cities in São Paulo state. Visiting early morning or late afternoon works best when the sun is less intense and the surf becomes more visible.

The name comes from ocean winds that blow regularly through the bay and shape the waves. These winds also influence the climate of the neighboring district, often bringing moist air from the ocean.