[3] 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.

In Brazil, both the cape and the mouth of the Oyapock are often mistaken for the whole country's northernmost point (rather than just of its coastline), and in the past this information could even be found in geography schoolbooks.

[4] Yet the true northernmost point in Brazil is actually far inland, on Monte Caburaí, in the state of Roraima, hundreds of kilometers from the Oyapock and almost a full degree more to the north.

It is the first international land border connection of French Guiana; although completed since 2011, as of February 2017, it had remained closed to traffic due to payment delays for construction and building crews, staffing issues within the Brazilian customs facilities, plus some minor disagreements between the Brazilian and French governments.

[7] The widespread Brazilian Portuguese expression "do Oiapoque ao Chuí" ("from the Oyapock to the Chuí [rivers]") is used to refer to the whole nation, by mentioning the waterways that mark respectively the northern and southern extremities of the Brazilian coastline (as noted above, they are often mistaken for the entire country's northern and southern extreme points).