The Mexican Revolution (Spanish: Revolución mexicana) was an extended sequence of armed regional conflicts in Mexico from 20 November 1910 to 1 December 1920. It has been called "the defining event of modern Mexican history". It saw the destruction of the Federal Army, its replacement by a revolutionary army, and the transformation of Mexican culture and government. The northern Constitutionalist faction prevailed on the battlefield and drafted the present-day Constitution of Mexico, which aimed to create a strong central government. Revolutionary generals held power from 1920 to 1940. The revolutionary conflict was primarily a civil war, but foreign powers, having important economic and strategic interests in Mexico, figured in the outcome of Mexico's power struggles; the U.S. involvement was particularly high. The conflict led to the deaths of around one million people, mostly non-combatants.

Although the decades-long regime of President Porfirio Díaz (1876–1911) was increasingly unpopular, there was no foreboding in 1910 that a revolution was about to break out. The aging Díaz failed to find a controlled solution to presidential succession, resulting in a power struggle among competing elites and the middle classes, which occurred during a period of intense labor unrest, exemplified by the Cananea and Río Blanco strikes. When wealthy northern landowner Francisco I. Madero challenged Díaz in the 1910 presidential election and Díaz jailed him, Madero called for an armed uprising against Díaz in the Plan of San Luis Potosí. Rebellions broke out first in Morelos (immediately south of the nation's capital city) and then to a much greater extent in northern Mexico. The Federal Army could not suppress the widespread uprisings, showing the military's weakness and encouraging the rebels. Díaz resigned in May 1911 and went into exile, an interim government was installed until elections could be held, the Federal Army was retained, and revolutionary forces demobilized. The first phase of the Revolution was relatively bloodless and short-lived.

Madero was elected President, taking office in November 1911. He immediately faced the armed rebellion of Emiliano Zapata in Morelos, where peasants demanded rapid action on agrarian reform. Politically inexperienced, Madero's government was fragile, and further regional rebellions broke out. In February 1913, prominent army generals from the former Díaz regime staged a coup d'etat in Mexico City, forcing Madero and Vice President Pino Suárez to resign. Days later, both men were assassinated by orders of the new President, Victoriano Huerta. This initiated a new and bloody phase of the Revolution, as a coalition of northerners opposed to the counter-revolutionary regime of Huerta, the Constitutionalist Army led by the Governor of Coahuila Venustiano Carranza, entered the conflict. Zapata's forces continued their armed rebellion in Morelos. Huerta's regime lasted from February 1913 to July 1914, and the Federal Army was defeated by revolutionary armies. The revolutionary armies then fought each other, with the Constitutionalist faction under Carranza defeating the army of former ally Francisco "Pancho" Villa by the summer of 1915.

Carranza consolidated power and a new constitution was promulgated in February 1917. The Mexican Constitution of 1917 established universal male suffrage, promoted secularism, workers' rights, economic nationalism, and land reform, and enhanced the power of the federal government. Carranza became President of Mexico in 1917, serving a term ending in 1920. He attempted to impose a civilian successor, prompting northern revolutionary generals to rebel. Carranza fled Mexico City and was killed. From 1920 to 1940, revolutionary generals held the office of president, each completing their terms (except from 1928-1934). This was a period when state power became more centralized, and revolutionary reform implemented, bringing the military under the civilian government's control. The Revolution was a decade-long civil war, with new political leadership that gained power and legitimacy through their participation in revolutionary conflicts. The political party those leaders founded in 1929, which would become the Institutional Revolutionary Party (PRI), ruled Mexico until the presidential election of 2000. When the Revolution ended is not well defined, and even the conservative winner of the 2000 election, Vicente Fox, contended his election was heir to the 1910 democratic election of Francisco Madero, thereby claiming the heritage and legitimacy of the Revolution.

Liberal general and war veteran Porfirio Díaz came to the presidency of Mexico in 1876 and remained almost continuously in office until 1911 in an era now called Porfiriato. Coming to power after a coup to oppose the re-election of Sebastián Lerdo de Tejada, he could not run for re-election in 1880. His close ally, General Manuel González, was elected president (1880–1884). Díaz saw himself as indispensable, and after that interruption, he ran for the presidency again and served in office continuously until 1911. The constitution had been amended to allow unlimited presidential re-election. During the Porfiriato, there were regular elections, widely considered sham exercises, marked by contentious irregularities.

In his early years in the presidency, Díaz consolidated power by playing opposing factions against each other and by expanding the Rurales, a force of armed and mounted police directly under his control that seized land from local peasants. Peasants were forced to make futile attempts to win back their land through courts and petitions. By 1900, over ninety percent of Mexico's communal lands were sold, with an estimated 9.5 million peasants forced into the service of wealthy landowners or hacendados. Diaz rigged elections, arguing that only he knew what was best for his country, and he enforced his belief with a strong hand. "Order and Progress" were the watchwords of his rule.

Díaz's presidency was characterized by the promotion of industry and the development of infrastructure by opening the country to foreign investment. Díaz suppressed opposition and promoted stability to reassure foreign investors. Farmers and peasants both complained of oppression and exploitation. The situation was further exacerbated by the drought that lasted from 1907 to 1909. The economy took a great leap during the Porfiriato, through the construction of factories, industries and infrastructure such as railroads and dams, as well as improving agriculture. Foreign investors bought large tracts of land to cultivate crops and range cattle for export. The cultivation of exportable goods such as coffee, tobacco, henequen for cordage, and sugar replaced the domestic production of wheat, corn and livestock that peasants had lived on. Wealth, political power and access to education were concentrated among a handful of elite landholding families mainly of European and mixed descent. These hacendados controlled vast swaths of the country through their huge estates (for example, the Terrazas had one estate in Sonora that alone comprised more than a million acres). Many Mexicans became landless peasants laboring on these vast estates or industrial workers toiling long hours for low wages. Foreign companies (mostly from the United Kingdom, France, and the U.S.) also exercised influence in Mexico.

Díaz had legitimacy as a leader through his battlefield accomplishments. He knew that the long tradition of military intervention in politics and its resistance to civilian control would prove challenging to his remaining in power. He set about curbing the power of the military, reining in provincial military chieftains, and making them subordinate to the central government. He contended with a whole new group of generals who had fought for the liberal cause and who expected rewards for their services. He systematically dealt with them, providing some rivals with opportunities to enrich themselves, ensuring the loyalty of others with high salaries, and others were bought off by rewards of landed estates and redirecting their political ambitions. Military rivals who did not accept the alternatives often rebelled and were crushed. It took him some 15 years to complete the transformation, reducing the army by 500 officers and 25 generals, creating an army subordinate to central power. He also created the military academy to train officers, but their training aimed to repel foreign invasions. Díaz expanded the rural police force, the rurales as an elite guard, including many former bandits, under the direct control of the president. With these forces, Díaz attempted to appease the Mexican countryside, led by a stable government that was nominally civilian, and the conditions to develop the country economically with the infusion of foreign investments.