1173

Events 
 Canonization of Saint Thomas à Becket, buried at Canterbury
 August 9th – Construction starts on the Leaning tower of Pisa
 Castle at Abergavenny was seized by the Welsh.
 Conversion to Christianity of Peter Waldo and the subsequent founding of the Waldensians.
 End of Qiandao era and start of Chunxi era of the Chinese emperor Xiaozong
 End of reign of Polish ruler Boleslaus IV of Poland and start of reign of Casimir II of Poland
 Eleanor of Aquitaine and her sons rebel against her husband Henry II of England in the Revolt of 1173-1174
 First recorded use of algebraic chess notation