French Guiana, officially just Guiana, is an overseas department and region of France, on the north Atlantic coast of South America. It borders Brazil to the east and south, and Suriname to the west. Its 83,534 km2 (32,253 sq mi) area has a very low population density of only 3 inhabitants per km2, with half of its 250,109 inhabitants in 2013 living in the metropolitan area of Cayenne, its capital. By land area, it is by far the largest overseas region of France. As an overseas region, it is inside the European Union, and its official currency is the Euro.

The addition of the adjective "French" in English comes from colonial times when five such colonies existed (The Guianas), namely from west to east: Spanish Guiana (now Guayana Region in Venezuela), British Guiana (now Guyana), Dutch Guiana (now Suriname), French Guiana, and Portuguese Guiana (now Amapá, a state in far northern Brazil). French Guiana and the two larger countries to the north and west, Guyana and Suriname, are still often collectively referred to as the Guianas and comprise one large shield landmass.

A large part of the department's economy derives from the presence of the Guiana Space Centre, now the European Space Agency's primary launch site near the equator.