The Battle of the Alamo (February 23 March 6, 1836) was a pivotal event in the Texas Revolution. Following a 13-day siege, Mexican troops under President General Antonio Lpez de Santa Anna reclaimed the Alamo Mission near San Antonio de Bxar (modern-day San Antonio, Texas, United States), killing most of the Texians and Tejanos inside. Santa Anna's cruelty during the battle inspired many Texians and Tejanos to join the Texian Army. Buoyed by a desire for revenge, the Texians defeated the Mexican Army at the Battle of San Jacinto, on April 21, 1836, ending the rebellion in favor of the newly formed Republic of Texas.

Several months previously, Texians had driven all Mexican troops out of Mexican Texas. About 100 Texians were then garrisoned at the Alamo. The Texian force grew slightly with the arrival of reinforcements led by eventual Alamo co-commanders James Bowie and William B. Travis. On February 23, approximately 1,500 Mexicans marched into San Antonio de Bxar as the first step in a campaign to retake Texas. For the next 10 days, the two armies engaged in several skirmishes with minimal casualties. Aware that his garrison could not withstand an attack by such a large force, Travis wrote multiple letters pleading for more men and supplies from Texas and from the United States, but the Texians were reinforced by fewer than 100 men because the United States had a treaty with Mexico, and supplying men and weapons would have been an overt act of war.

In the early morning hours of March 6, the Mexican Army advanced on the Alamo. After repelling two attacks, the Texians were unable to fend off a third attack. As Mexican soldiers scaled the walls, most of the Texian fighters withdrew into interior buildings. Occupiers unable to reach these points were slain by the Mexican cavalry as they attempted to escape. Between five and seven Texians may have surrendered; if so, they were quickly executed. Several noncombatants were sent to Gonzales to spread word of the Texian defeat. The news sparked both a strong rush to join the Texian army and a panic, known as "The Runaway Scrape", in which the Texian army, most settlers, and the government of the new, self-proclaimed but officially unrecognized Republic of Texas fled eastward toward the U.S. ahead of the advancing Mexican Army.

Within Mexico, the battle has often been overshadowed by events from the MexicanAmerican War of 18461848. In 19th-century Texas, the Alamo complex gradually became known as a battle site rather than a former mission. The Texas Legislature purchased the land and buildings in the early part of the 20th century and designated the Alamo chapel as an official Texas State Shrine. The Alamo has been the subject of numerous non-fiction works beginning in 1843. Most Americans, however, are more familiar with the myths and legends spread by many of the movie and television adaptations, including the 1950s Disney mini-series Davy Crockett and John Wayne's 1960 film The Alamo.

The Texas Revolution (October 2, 1835 – April 21, 1836) was a rebellion of colonists from the United States and Tejanos (Hispanic Texans) in putting up armed resistance to the centralist government of Mexico. While the uprising was part of a larger one, the Mexican Federalist War, that included other provinces opposed to the regime of President Antonio López de Santa Anna, the Mexican government believed the United States had instigated the Texas insurrection with the goal of annexation. The Mexican Congress passed the Tornel Decree, declaring that any foreigners fighting against Mexican troops "will be deemed pirates and dealt with as such, being citizens of no nation presently at war with the Republic and fighting under no recognized flag". Only the province of Texas succeeded in breaking with Mexico, establishing the Republic of Texas, and eventually being annexed by the United States.

The revolution began in October 1835, after a decade of political and cultural clashes between the Mexican government and the increasingly large population of American settlers in Texas. The Mexican government had become increasingly centralized and the rights of its citizens had become increasingly curtailed, particularly regarding immigration from the United States. Mexico had officially abolished slavery in Texas in 1830, and the desire of Anglo Texans to maintain the institution of chattel slavery in Texas was also a major cause of secession. Colonists and Tejanos disagreed on whether the ultimate goal was independence or a return to the Mexican Constitution of 1824. While delegates at the Consultation (provisional government) debated the war's motives, Texians and a flood of volunteers from the United States defeated the small garrisons of Mexican soldiers by mid-December 1835. The Consultation declined to declare independence and installed an interim government, whose infighting led to political paralysis and a dearth of effective governance in Texas. An ill-conceived proposal to invade Matamoros siphoned much-needed volunteers and provisions from the fledgling Texian Army. In March 1836, a second political convention declared independence and appointed leadership for the new Republic of Texas.

Determined to avenge Mexico's honor, Santa Anna vowed to personally retake Texas. His Army of Operations entered Texas in mid-February 1836 and found the Texians completely unprepared. Mexican General José de Urrea led a contingent of troops on the Goliad Campaign up the Texas coast, defeating all Texian troops in his path and executing most of those who surrendered. Santa Anna led a larger force to San Antonio de Béxar (or Béxar), where his troops defeated the Texian garrison in the Battle of the Alamo, killing almost all of the defenders.

A newly created Texian army under the command of Sam Houston was constantly on the move, while terrified civilians fled with the army, in a melee known as the Runaway Scrape. On March 31, Houston paused his men at Groce's Landing on the Brazos River, and for the next two weeks, the Texians received rigorous military training. Becoming complacent and underestimating the strength of his foes, Santa Anna further subdivided his troops. On April 21, Houston's army staged a surprise assault on Santa Anna and his vanguard force at the Battle of San Jacinto. The Mexican troops were quickly routed, and vengeful Texians executed many who tried to surrender. Santa Anna was taken hostage; in exchange for his life, he ordered the Mexican army to retreat south of the Rio Grande. Mexico refused to recognize the Republic of Texas, and intermittent conflicts between the two countries continued into the 1840s. The annexation of Texas as the 28th state of the United States, in 1845, led directly to the Mexican–American War.