Cayenne is the capital 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".

At the 2006 census, there were 100,323 inhabitants in the urban area of Cayenne (as defined by INSEE), 50,594 of whom lived in the city (commune) of Cayenne proper, and the remainder in the neighbouring commune of Remire-Montjoly. The commune of Matoury (18,032 inhabitants in 1999), where Cayenne-Rochambeau Airport is located, is also a suburb of Cayenne, but it was not included in the official definition of the urban area by INSEE in 1999.

Cayenne is a coastal town Atlantic Guyana. Located on the banks of the estuary of the Cayenne River, the town occupies part of the Ile de Cayenne.

Cayenne centres on its main commercial street, the Avenue Général de Gaulle. At the east end of the avenue near the coast is the Place de Palmistes and the Place de Grenoble (also known as the Place Léopold Héder). Most of the official buildings are located in this area: the Hôtel de Ville (the town hall) built by Jesuits in the 1890s, the Post Office, the Préfecture, residence of French Guiana's Préfect, and the Musée Départmental Franconie. To the west of this area lies Fort Cépérou, built in the 17th century, though now mostly in ruins. To the south lie the Place du Coq and Place Victor Schoelcher (named in honour of the anti-slavery activist) and a market.

To the south of this compact region is the Village Chinois (known as Chicago), separated from the rest of Cayenne by the Canal Laussat. It has a reputation for being a dangerous area.

Other buildings in the city include the Cathédrale Saint-Sauveur de Cayenne, municipal library, the municipal museum and a museum of French Guianese Culture (Musée des Cultures Guyanaise) and a scientific research institute (IRD or Institut de recherche pour le développement, formerly Orstom). The Jardin botanique de Cayenne is the city's botanical garden.

There are some beaches along the coast, like Montjoly and Montabo, and several promontories, though the waters contain sharks.