First Crusade: Around 800 Jews are massacred in Worms, Germany.

The First Crusade (1096–1099) was the first of a series of religious wars, or Crusades, which were initiated, supported and at times directed by the Latin Church in the Middle Ages. Their aim was to return the Holy Land—which had been conquered by the Rashidun Caliphate in the 7th century—to Christian rule. By the 11th century, although Jerusalem had then been ruled by Muslims for hundreds of years, the practices of the Seljuk rulers in the region began to threaten local Christian populations, pilgrimages from the West and the Byzantine Empire itself. The earliest impetus for the First Crusade came in 1095 when Byzantine emperor Alexios I Komnenos sent ambassadors to the Council of Piacenza to request military support in the empire's conflict with the Seljuk-led Turks. This was followed later in the year by the Council of Clermont, at which Pope Urban II gave a speech supporting the Byzantine request and urging faithful Christians to undertake an armed pilgrimage to Jerusalem.

The Worms massacre was the murder of at least 800 to 1000 Jews from Worms, Holy Roman Empire, during the events of the First Crusade under Count Emicho in May, 18-25 1096. This massacre is a part of series of mass murders of Jews that happen in the Rhineland Jewish communities that known as The Rhineland massacres or Gzerot Tatnó.

May 18 is the 138th day of the year in the Gregorian calendar; 227 days remain until the end of the year.