The Oyapock or Oiapoque is a 403-kilometre (250 mi) long river in South America that forms most of the border between the French overseas department of French Guiana and the Brazilian state of Amapá.

Amapá ( ) is one of the 26 states of Brazil. It is in the North Region of Brazil. It is the second-least populous state and the eighteenth-largest state by area. Located in the far northern part of the country, Amapá is bordered clockwise by French Guiana to the north for 730 km, the Atlantic Ocean to the east for 578 km, Pará to the south and west, and Suriname to the northwest for 63 km. The capital and largest city is Macapá. The state has 0.4% of the Brazilian population and is responsible for only 0.22% of the Brazilian GDP.