New Spain comprised much of the Spanish possessions in the New World during the colonial period. At its height, New Spain included what are today the southwestern United States, all of Mexico, Central America to the Isthmus of Panama, Florida, much of the West Indies (islands in the Caribbean), as well as the Philippines in the Pacific Ocean. The viceroyalty (province governed by a representative of the monarch) was governed from the capital at Mexico City beginning in 1535. In 1821 a Mexican rebellion ended Spanish rule there, and the colonial empire of New Spain was dissolved. By 1898 Spain had relinquished all its possessions in North America. Its last holdings were the islands of Cuba, Puerto Rico, Guam, and the Philippines, which were ceded to the United States after Spain lost the Spanish-American War (1898).

During the colonial period, Spain also claimed other territories in the New World—in northern and western South America. Most of these holdings fell under the viceroyalty of Peru, which was administered separately from the viceroyalty of New Spain. These possessions were also lost by Spain by the end of the 1800s.