Juan O'Donojú in the context of "Viceroy"

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.

Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually defined as consisting of seven countries: Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama. Within Central America is the Mesoamerican biodiversity hotspot, which extends from southern Mexico to southeastern Panama. Due to the presence of several active geologic faults and the Central America Volcanic Arc, there is a high amount of seismic activity in the region, such as volcanic eruptions and earthquakes, which has resulted in death, injury, and property damage.

Most of Central America falls under the Isthmo-Colombian cultural area. Before the Spanish expedition of Christopher Columbus' voyages to the Americas, hundreds of indigenous peoples made their homes in the area. From the year 1502 onwards, Spain began their colonization. From 1609 to 1821, the majority of Central American territories (except for what would become Belize and Panama and including the modern Mexican state of Chiapas) were governed by the viceroyalty of New Spain from Mexico City as the Captaincy General of Guatemala. On 24 August 1821, Spanish Viceroy Juan de O'Donojú signed the Treaty of Córdoba, which established New Spain's independence and autonomy from mainland Spain. On 15 September, the Act of Independence of Central America was enacted to announce Central America's separation from the Spanish Empire. Some of New Spain's provinces in the Central American region were invaded and annexed to the First Mexican Empire; however in 1823 they seceded from Mexico to form the Federal Republic of Central America until 1838.

The Plan of Iguala, also known as the Plan of the Three Guarantees ("Plan Trigarante") or Act of Independence of North America, was a revolutionary proclamation promulgated on 24 February 1821, in the final stage of the Mexican War of Independence from Spain. The Plan stated that Mexico was to become a constitutional monarchy, whose sole official religion would be Roman Catholicism, in which both the Peninsulares (people born in Spain and residing in Mexico) and the Americanos (people born in Mexico, that is, the Americas) would enjoy equal political and social rights. It took its name from the city of Iguala in the modern-day state of Guerrero.

The two main figures behind the Plan were Agustín de Iturbide (who would become Emperor of Mexico) and Vicente Guerrero, revolutionary rebel leader and later President of Mexico. The Army of the Three Guarantees was formed by the unified forces of Iturbide and Guerrero to defend the ideals of the Plan of Iguala. On 24 August 1821, Iturbide and Spanish viceroy Juan O'Donojú signed the Treaty of Córdoba in Córdoba, Veracruz, ratifying the Plan of Iguala, and thus confirming Mexico's independence.

The Treaty of Córdoba established Mexican independence from Spain at the conclusion of the Mexican War of Independence. It was signed on August 24, 1821 in Córdoba, Veracruz, Mexico. The signatories were the head of the Army of the Three Guarantees, Agustín de Iturbide, and, acting on behalf of the Spanish government, Jefe Político Superior Juan O'Donojú. The treaty has 17 articles, which developed the proposals of the Plan of Iguala. The Treaty is the first document in which Spanish (without authorization) and Mexican officials accept the liberty of what will become the First Mexican Empire, but it is not today recognized as the foundational moment, since these ideas are often attributed to the Grito de Dolores (September 16, 1810). The treaty was rejected by the Spanish government, publishing this determination in Madrid on February 13 and 14, 1822.