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 López de Santa Anna reclaimed the Alamo Mission near San Antonio de Béxar (modern-day San Antonio, Texas, United States), killing the Texian and immigrant occupiers. Santa Anna's cruelty during the battle inspired many Texians, both legal Texas settlers and illegal immigrants from the United States, 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.

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 Béxar 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. Most eyewitness accounts reported between 182 and 257 Texians died, while most historians of the Alamo agree that around 600 Mexicans were killed or wounded. 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 new, self-proclaimed but officially unrecognized, Republic of Texas government fled eastward toward the United States ahead of the advancing Mexican Army.