The First Mexican Republic, known also as the First Federal Republic (Spanish: Primera República Federal), is a federated republic and nation-state officially designated the United Mexican States (Spanish: Estados Unidos Mexicanos).

The First Mexican Republic lasts from 1824 to 1835, when conservatives under Antonio López de Santa Anna transform it into a centralized state, the Centralist Republic of Mexico.

The republic is proclaimed on November 1, 1823 by the Constituent Congress, months after the fall of the Mexican Empire ruled by emperor Agustin I, a former royalist military officer-turned-insurgent for independence.

The federation is formally and legally established on October 4, 1824 when the Federal Constitution of the United Mexican States comes into force.

It is bordered on the north by the United States and Oregon Country (or Columbia District); on the south and west by the Pacific Ocean; on the southeast by Federal Republic of Central America, and the Caribbean Sea; and on the east by the Gulf of Mexico.

The Federal Republic lasts almost twelve years with constant struggles between the main political parties: the Conservatives, landowners and former monarchists, favoring a strong central government and a confessional state; and the Liberals, republicans favoring a limited government power divided among the federated states and a secular nation.

The conflict causes severe political instability and violence.

The republic is ruled by two triumvirates and nine presidents.

Guadalupe Victoria is the only president who completes his full term in this period and in almost thirty years of independent Mexico.

On October 23, 1835, after the repeal of the Constitution of 1824, the Federal Republic is changed to a Centralist Republic.

The unitary regime is formally established on December 30, 1836, with the enactment of the seven constitutional laws