The Waco siege, also known as the Waco massacre, was the law enforcement siege of the compound that belonged to the religious sect Branch Davidians. It was carried out by the U.S. federal government, Texas state law enforcement, and the U.S. military, between February 28 and April 19, 1993. The Branch Davidians were led by David Koresh and were headquartered at Mount Carmel Center ranch in the community of Axtell, Texas, 13 miles (21 kilometers) northeast of Waco. Suspecting the group of stockpiling illegal weapons, the Bureau of Alcohol, Tobacco, and Firearms (ATF) obtained a search warrant for the compound and arrest warrants for Koresh, as well as a select few of the group's members.

The incident began when the ATF attempted to serve a search and arrest warrant on the ranch. An intense gunfight erupted, resulting in the deaths of four government agents and six Branch Davidians. Upon the ATF's entering of the property and failure to execute the search warrant, a siege lasting 51 days was initiated by the Federal Bureau of Investigation (FBI). Eventually, the FBI launched an assault and initiated a tear gas attack in an attempt to force the Branch Davidians out of the ranch. Shortly thereafter, the Mount Carmel Center became engulfed in flames. The fire resulted in the deaths of 76 Branch Davidians, including 25 children, two pregnant women, and David Koresh himself.The events of the siege and attack are disputed by various sources. A particular controversy ensued over the origin of the fire; an internal Justice Department investigation concluded in 2000 that incendiary tear gas canisters were used by the FBI, but maintained that sect members had started the fire. This came after a panel of arson investigators concluded that the Davidians were responsible for igniting it simultaneously in at least three different areas of the compound. The events near Waco, along with the law enforcement siege at Ruby Ridge less than 12 months earlier, have been cited by commentators as catalysts for the Oklahoma City bombing by Timothy McVeigh and Terry Nichols, as well as the modern day American militia movement and a rise in opposition to firearm regulation.