The Worms massacre was the murder of at least 800 Jews from Worms, Holy Roman Empire (now Germany), at the hands of crusaders under Count Emicho in May 1096.

The massacre at Worms was one of a number of attacks against Jewish communities perpetrated during the First Crusade (10961099). Followers of Count Emicho arrived at Worms on May 18, 1096. Soon after his arrival, a rumour spread that the Jews had boiled a Christian alive, and used his corpse to contaminate water to poison the town's wells. The local populace later joined forces with Emicho and launched a savage attack on the town's Jews, who had been given sanctuary in Bishop Adalbert's palace, though others chose to remain outside its walls. They were the first to be massacred.After eight days, Emicho's army, assisted by local burghers broke in and slaughtered those seeking asylum there. The Jews were in the midst of reciting the Hallel prayer for Rosh Chodesh Sivan.In all, from 800 to 1,000 Jews were killed, with the exception of some who committed suicide and a few who were forcibly baptised. One, Simchah ben Yitzchak ha-Cohen, stabbed the bishop's nephew while being baptised and was consequently killed. One of the most famous victims was Minna of Worms.

The First Crusade (1096–1099) was the first of a series of religious wars, or Crusades, initiated, supported and at times directed by the Latin Church in the medieval period. The objective was the recovery of the Holy Land from Islamic rule. While Jerusalem had been under Muslim rule for hundreds of years, by the 11th century the Seljuk takeover of the region threatened local Christian populations, pilgrimages from the West, and the Byzantine Empire itself. The earliest initiative for the First Crusade began in 1095 when Byzantine emperor Alexios I Komnenos requested military support from the Council of Piacenza in the empire's conflict with the Seljuk-led Turks. This was followed later in the year by the Council of Clermont, during which Pope Urban II supported the Byzantine request for military assistance and also urged faithful Christians to undertake an armed pilgrimage to Jerusalem.

This call was met with an enthusiastic popular response across all social classes in western Europe. Mobs of predominantly poor Christians numbering in the thousands, led by Peter the Hermit, a French priest, were the first to respond. What has become known as the People's Crusade passed through Germany and indulged in wide-ranging anti-Jewish activities, including the Rhineland massacres. On leaving Byzantine-controlled territory in Anatolia, they were annihilated in a Turkish ambush led by the Seljuk Kilij Arslan at the Battle of Civetot in October 1096.

In what has become known as the Princes' Crusade, members of the high nobility and their followers embarked in late-summer 1096 and arrived at Constantinople between November and April the following year. This was a large feudal host led by notable Western European princes: southern French forces under Raymond IV of Toulouse and Adhemar of Le Puy; men from Upper and Lower Lorraine led by Godfrey of Bouillon and his brother Baldwin of Boulogne; Italo-Norman forces led by Bohemond of Taranto and his nephew Tancred; as well as various contingents consisting of northern French and Flemish forces under Robert Curthose (Robert II of Normandy), Stephen of Blois, Hugh of Vermandois, and Robert II of Flanders. In total and including non-combatants, the forces are estimated to have numbered as many as 100,000.

The crusaders marched into Anatolia. With Kilij Arslan absent, a Frankish attack and Byzantine naval assault during the Siege of Nicea in June 1097 resulted in an initial victory for the crusaders. In July, the crusaders won the Battle of Dorylaeum, fighting Turkish lightly-armoured mounted archers. Next the crusaders marched through Anatolia, suffering casualties from starvation, thirst, and disease. The decisive and bloody Siege of Antioch was fought beginning in 1097 and the city was captured by the crusaders in June 1098. Jerusalem was reached in June 1099 and the Siege of Jerusalem resulted in the city being taken by assault from 7 June to 15 July 1099, during which its defenders were ruthlessly massacred. The Kingdom of Jerusalem was established as a secular state under the rule of Godfrey of Bouillon, who shunned the title of "king". A counterattack was repulsed that year at the Battle of Ascalon, ending the First Crusade. Afterwards the majority of the crusaders returned home.

Four Crusader states were established in the Holy Land: the Kingdom of Jerusalem, the County of Edessa, the Principality of Antioch, and the County of Tripoli. The Crusader presence remained in the region in some form until the loss of the last major Crusader stronghold in the Siege of Acre in 1291. After this loss of all Crusader territory in the Levant, there were no further substantive attempts to recover the Holy Land.