The two islands of Saint Kitts and Nevis, which are both in the West Indies and are part of the Leeward Islands chain of the Lesser Antilles, make up the island country and microstate of Saint Kitts and Nevis, which is officially known as the Federation of Saint Christopher and Nevis. It is the world's smallest sovereign federation and the smallest sovereign state in the Western Hemisphere, both in terms of area and population, with 261 square kilometers of territory and approximately 50,000 people. Charles III is the monarch and head of state in this Commonwealth realm. In the Caribbean, it is the only sovereign federation.

Basseterre is the capital of the larger island of Saint Kitts. Additionally, Basseterre is the primary port of entry for cargo and passengers (via cruise ships). Through a narrow channel known as The Narrows, the smaller island of Nevis is approximately 3 km (2 mi) southeast of Saint Kitts.

In the past, this union was also comprised of the British dependency of Anguilla, which was collectively referred to as Saint Christopher-Nevis-Anguilla. However, Anguilla made the decision to break away from the union and is still an overseas British territory. To the north-northwest of the country are the islands of Anguilla, Saint Barthelemy, Saint-Martin/Sint Maarten, and Sint Eustatius. Toward the east and upper east are Antigua and Barbuda, and toward the southeast is the little uninhabited island of Redonda (part of Antigua and Barbuda) and the island of Montserrat.

One of the first islands in the Caribbean to be colonized by Europeans was Saint Kitts and Nevis. "The Mother Colony of the West Indies" also applies to Saint Kitts and Nevis because it was the site of the first British and French Caribbean colonies. It also became independent in 1983, making it the most recent British territory in the Caribbean to do so.