The United Mexican States commonly known as Mexico is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of Mexico. Covering almost 2 million square kilometres, Mexico is the fifth-largest country in the Americas by total area and the 14th largest independent nation in the world. With an estimated population of 109 million, it is the 11th most populous country. Mexico is a federation comprising thirty-one states and a Federal District, the capital city.