Oyapok River

The Oyapock or Oiapoque River (/ˈɔɪəpɒk/ or /ɔɪəˈpoʊkiː/; French: Fleuve Oyapock [flœv wɑjapɔk]; Portuguese: Rio Oiapoque [ˈʁiu ɔjɐˈpɔki]) is a 370-km (230-mi)–long river in South America that forms most of the border between French Guiana and the Brazilian state of Amapá.

The Oyapock runs through the Guianan moist forests ecoregion. It rises in the Tumuk Humak (Portuguese: Tumucumaque) mountain range and flows into the Atlantic Ocean, where its estuary forms a large bay bordering on Cape Orange.