The Mexican Empire was a constitutional monarchy, the first independent government of Mexico and the only former viceroyalty of the Spanish Empire to establish a monarchy after independence. It lasted for 2 years from 1821 to 1823. It is one of the few modern-era, independent monarchies that have existed in the Americas, along with the 67-year Empire of Brazil (1822–1889) and the 2-year First Empire of Haiti (1804–1806).

Juan José Rafael Teodomiro de O'Donojú y O'Ryan was a Spanish military officer, diplomat and Viceroy of New Spain (Mexico) from 21 July 1821 to 28 September 1821 during the Mexican War of Independence. He was the last Viceroy of New Spain.