1181

1181 (MCLXXXI) was a common year starting on Thursday of the Julian calendar, the 1181st year of the Common Era (CE) and Anno Domini (AD) designations, the 181st year of the 2nd millennium, the 81st year of the 12th century, and the 2nd year of the 1180s decade. As of the start of 1181, the Gregorian calendar was 7 days ahead of the Julian calendar, which was the dominant calendar of the time.

• Jayavarman VII defeats the Cham and assumes control of the Khmer kingdom.
• The word Albigensians first used by chronicler Geoffroy du Breuil of Vigeois to describe the inhabitants of Albi, France.
• September 1 — Pope Lucius III succeeds Pope Alexander III as the 171st pope.
• Chinese and Japanese astronomers observe what has since come to be understood as a supernova. One of only eight supernovae in the Milky Way observed in recorded history, it appeared in the constellation Cassiopeia and was visible in the night sky for about 185 days. The radio source 3C58 is thought to be the remnant from this event.
• Beginning of the Yowa era in Japan. The era is marked by famine.

• Saint Francis of Assisi, Italian founder of the Franciscan Order (died 1226)
• Saint Teresa of Portugal
• Jayavarman VII, king of the Khmer (died 1219)

• January 30 — Emperor Takakura of Japan (b. 1161)
• March 17 — Henry I of Champagne
• June 30 — Hugh de Kevelioc, 3rd Earl of Chester, English politician (b. 1147)
• August 30 — Pope Alexander III (b. c. 1100–1105)
• Taira no Kiyomori, Japanese warlord (b. 1118)
• As-Salih Ismail al-Malik, ruler of Syria (b. 1163)