The Rio Oiapoque is a 403-kilometre river in the far north of Amapá, Brazil, rising in the Tumucumaque mountain range and flowing northeast to empty into the Atlantic Ocean, where its estuary forms a large bay near Cape Orange. For its entire lower course, the river marks the international border between Brazil and the French overseas department of French Guiana, giving it a distinctive geopolitical character that paddlers should be aware of when planning any crossing or travel along its banks.

The river passes through the Guianan moist forests ecoregion, offering a landscape of dense Amazonian rainforest throughout much of its length. The current is notably strong in sections — strong enough that the visible power of the water is evident in videos of people attempting to swim across certain stretches. Rapids are present along the river, and body rafting through these sections occurs in the area. Paddlers should treat the current with serious respect, as conditions can be demanding.

The city of Oiapoque sits on the Brazilian bank of the river and serves as the primary hub for activity in the area. Traditional flat-bottomed boats known as Catraia are used locally for river crossings, carrying goods and passengers between the Brazilian and French Guianese sides. The Oyapock River Bridge, completed in 2011 and opened to traffic in 2017, connects Oiapoque with Saint-Georges on the French Guiana side. The river's proximity to the Cape Orange National Park, which covers over 6,500 square kilometres of coastal rainforest, adds ecological significance to the broader area. Oiapoque can be reached by air via the Oiapoque Airport, which is relevant for paddlers organizing logistics to this remote region.