Mexico (Spanish: México), officially known as the Mexican Empire (Spanish: Imperio Mexicano ), is a constitutional monarchy in North America. It is bordered on the north and by the west by the United States; on the south and west by the Pacific Ocean and Costa Rica; on the southeast by the Caribbean Sea; and on the east by the Gulf of Mexico. Covering almost two million sq km (over 760,000 sq mi), Mexico is the fifth-largest country in the Americas by total area and the seventh largest independent nation in the world. With an estimated population of 37 million, is the most populous Hispanophone country on Earth. Mexico is a federation comprising twenty states.