Saint Kitts and Nevis ( (listen)), officially the Federation of Saint Christopher and Nevis, is an island country in the West Indies. Located in the Leeward Islands chain of the Lesser Antilles, it is the smallest sovereign state in the Western Hemisphere, in both area and population, as well as the world's smallest sovereign federation. The country is a Commonwealth realm, with Elizabeth II as Queen and head of state. It is the only sovereign federation in the Caribbean.

The capital city is Basseterre, located on the larger island of Saint Kitts. Basseterre is also the main port for both passenger entry (via cruise ships) and cargo. The smaller island of Nevis lies approximately 3 km (2 mi) to the southeast of Saint Kitts, across a shallow channel called The Narrows.The British dependency of Anguilla was historically also a part of this union, which was then known collectively as Saint Christopher-Nevis-Anguilla. However, Anguilla chose to secede from the union and remains a British overseas territory. To the north-northwest lie the islands of Sint Eustatius, Saba, Saint Barthélemy, Saint-Martin/Sint Maarten and Anguilla. To the east and northeast are Antigua and Barbuda, and to the southeast is the small uninhabited island of Redonda (part of Antigua and Barbuda) and the island of Montserrat.

Saint Kitts and Nevis were among the first islands in the Caribbean to be colonized by Europeans. Saint Kitts was home to the first British and French colonies in the Caribbean, and thus has also been titled "The Mother Colony of the West Indies". It is also the most recent British territory in the Caribbean to become independent, gaining independence in 1983.