Overview
The year 1100 (MC) is most often referenced as the final year of the 11th century. In contemporary medieval Europe it was dated according to the Julian calendar; as a year divisible by four it was treated as a leap year under that system. The numbering of centuries means that 1100 is normally counted as the last year of the 11th century, while 1101 is the first year of the 12th century.
Notable events and successions
Several high-profile political changes occurred in 1100 that shaped medieval politics. In England, the death of William II (known as William Rufus) left a power vacuum quickly filled by his brother Henry, who secured the throne and was crowned soon afterward. In the Levant, the immediate aftermath of the First Crusade continued to rearrange local rule: Godfrey of Bouillon, the first ruler of the newly captured Jerusalem, died and was succeeded by his brother Baldwin, who consolidated the principality that became the Kingdom of Jerusalem.
Broader context
The year falls within an era of active territorial consolidation and cultural exchange: northern and western Europe were organizing increasingly centralized principalities under feudal norms, while in the eastern Mediterranean the crusader states and the Seljuk principalities adjusted to new political realities. In East Asia and elsewhere, established dynasties and trading networks continued to sustain long-distance contacts and technological transfer.
Calendar and legacy
1100 illustrates two common points of confusion in dating. First, the ordinal-number method for centuries places years ending in “00” at the close of the previous century rather than the start of the next. Second, later calendar reform affects how we view those years: the Julian system regarded 1100 as a leap year, whereas under the modern Gregorian rules a year divisible by 100 but not by 400 would not be a leap year. For historians the events of 1100 are useful markers of succession, state formation, and the transition between medieval centuries.