The Head of State in Mexico is the person who controls the executive power in the country. Under the current constitution, this responsibility lies with the President of the United Mexican States, who is head of the supreme executive power of the Mexican Union. Throughout its history, Mexico has had several forms of government. Under the federal constitutions, the title of President was the same as the current. Under the Seven Laws (centralist), the chief executive was named President of the Republic. In addition, there have been two periods of monarchical rule, during which the executive was controlled by the Emperor of Mexico.

The chronology of the heads of state of Mexico is complicated due to the country's political instability during the 19th and 20th centuries. With few exceptions, most of the Mexican presidents elected during this period did not complete their terms. Until the 1934-1940 tenure of Lázaro Cárdenas, each president had remained in office an average of 15 months.

Harry Turtledove has fictionalized the Mexican leadership as follows.

The Guns of the South

Mexico started out as an Empire in the 1820s before swiftly transitioning to a Republic. After four decades of unstable government and much loss of territory, the Republic was overthrown and the Second Empire was imposed upon Mexico by the French Intervention. While the United States intended to protect Mexican sovereignty and restore the Republic, the northern nation's injury in the Second American Revolution, and subsequent entanglement in another war farther north, left them unable to fulfill this promise.

Leader Term Title
Benito Juárez Juarez.jpg 1858-1864 President
Maximilian I Maximilian.jpg 1864-
Incumbent at novel's end, 1868

Southern Victory

See Emperor of Mexico#Southern Victory

Other Heads of State

Antonio Lopez de Santa Anna is referenced as a living former President in "Lee at the Alamo."