Cayenne is the prefecture of French Guiana, an overseas region and department of France located in South America. The city stands on a former island at the mouth of the Cayenne River on the Atlantic coast. The city's motto is "fert aurum industria", which means "work brings wealth". Cayenne is the largest Francophone city of the South American continent.

The Portuguese conquest of French Guiana, also known as Conquest of Cayenne, was a military operation against Cayenne, capital of the South American colony of French Guiana, launched in January 1809 in the context of the Napoleonic Wars. The invasion was undertaken by a combined expeditionary force that included Portuguese and British military contingents.