The Federal Constitution of the United Mexican States of 1857, often called simply the Constitution of 1857, was the liberal constitution promulgated in 1857 by Constituent Congress of Mexico during the presidency of Ignacio Comonfort. Ratified on February 5, 1857, the constitution established individual rights, including universal male suffrage, and others such as freedom of speech, freedom of conscience, freedom of the press, freedom of assembly, and the right to bear arms. It also reaffirmed the abolition of slavery, debtors' prisons, and all forms of cruel and unusual punishment such as the death penalty. The constitution was designed to guarantee a limited central government by federalism and created a strong national congress, an independent judiciary, and a small executive to prevent a dictatorship. Liberal ideals meant the constitution emphasized private property of individuals and sought to abolish common ownership by corporate entities, mainly the Catholic Church and indigenous communities, incorporating the legal thrust of the Lerdo Law into the constitution.

Liberalism in Mexico was part of a broader nineteenth-century political trend affecting Western Europe and the Americas, including the United States, that challenged entrenched power. In Mexico, liberalism sought to make fundamental the equality of individuals before the law, rather than their benefiting from special privileges of corporate entities, especially the Roman Catholic Church, the military, and indigenous communities. Liberalism viewed universal, free, secular education as the means to transform Mexico's citizenry. Early nineteenth-century liberals promoted the idea of economic development in the overwhelmingly rural country where much land was owned by the Catholic Church and held in common by indigenous communities to create a large class of yeoman farmers. Liberals passed a series of individual Reform laws and then wrote a new constitution in 1857 to give full force to the changes. Liberalism in Mexico "was not only a political philosophy of republicanism but a package including democratic social values, free enterprise, a legal bundle of civil rights to protect individualism, and a group consciousness of nationalism." Mexican liberalism is most closely associated with anticlericalism. Mexican liberals looked to the U.S. as their model for development and actively sought the support of the U.S., while Mexican conservatives looked to Europe.