The Mexican Empire (Spanish: Imperio Mexicano, pronounced [imˈpeɾjo mexiˈkano] ) was a constitutional monarchy and the first independent government of Mexico. It was also the only former viceroyalty of the Spanish Empire to establish a monarchy after gaining independence. The empire existed from 1821 to 1823, making it one of the few modern-era independent monarchies in the Americas. To distinguish it from the later Second Mexican Empire (1864–1867) under Emperor Maximilian, this historical period is commonly referred to as the First Mexican Empire. The empire was led by former Royal Spanish military officer Agustín de Iturbide, who ruled as Agustín I.
The establishment of a monarchy was the initial goal for an independent Mexico, as outlined in the Plan of Iguala, a political document drafted by Iturbide that unified the forces fighting for independence from Spain. Following the signing of the Treaty of Córdoba by the last Spanish viceroy in September 1821, the plan for a Mexican monarchy advanced. Iturbide's popularity reached its peak on May 18, 1822, when public demonstrations called for him to become emperor in the absence of a European royal willing to assume the throne. The Mexican Congress approved the proposal, and Iturbide was crowned in July 1822.