The Federal Constitution of the United Mexican States of 1857 (Spanish: Constitución Federal de los Estados Unidos Mexicanos de 1857) often called simply the Constitution of 1857 is the liberal constitution drafted by 1857 Constituent Congress of Mexico during the presidency of Ignacio Comonfort. It was ratified on February 5, 1857,establishing individual rights 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, eliminated debtor prison, and eliminated all forms of cruel and unusual punishment, including the death penalty.

Some articles were contrary to the interests of the Catholic Church, such as education free of dogma, the removal of institutional fueros (privileges) and the sale of property belonging to the church. The Conservative Party strongly opposed the enactment of the new constitution and this polarized Mexican society. The Reform War began as a result, and the struggles between liberals and conservatives were intensified with the implementation of the Second Mexican Empire under the support of the church. Years later, with the restored republic, the Constitution was in force throughout the country until 1917.