What is the Oyapock River?

Oyapock River or Oiapoque River (Portuguese: Rio Oiapoque; French: Oyapock) is a river of eastern French Guiana and northern Amapá, Brazil, along the border between France and Brazil.

It is the largest river in French Guiana, with a total drainage area of over 20,000 square kilometres. The river begins in the Tumuc Humac Mountains (Montes Tumuc-Humac) and flows northward for 450 kilometres before entering the Atlantic Ocean east of the city of Oiapoque.

The river is fed by heavy rainfall in the region; it has many waterfalls and rapids, which are not navigable. This lack of navigability has contributed to the area's isolation and undeveloped status, despite its rich mineral and forest resources.