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|Births – Deaths|
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|Establishments – Disestablishments|
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|1170 in poetry|
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- September 21 – Following a siege, combined Anglo-Norman and Irish forces seize the city of Dublin, forcing Ascall mac Ragnaill, King of Dublin, into exile.
- November (or December) – Henry II of England, when word reaches him in France of Thomas Becket's latest actions, utters words that are interpreted by his followers as a wish for the archbishop's death.
- December 29 – Thomas Becket, Archbishop of Canterbury, is assassinated in Canterbury Cathedral.
- The Danes attack Estonia.
- The East Frisian island of Bant is broken up in a North Sea flood.
- Palace guards massacre the civil officials at the Korean court, and place a new king on the throne. The coup leaders abolish the privileges that have kept the aristocrats in power, and appoint themselves to senior posts.
- Earliest date for the making of Cheddar cheese.
- According to folklore, the Welsh prince Madoc sails to North America, in his ship the Gwennan Gorn, and founds a colony.
- Estimation: Fes in the Almohad Empire becomes the largest city of the world, taking the lead from Constantinople, capital of the Byzantine Empire.
- May 9 (or June 28) – Valdemar II of Denmark (d. 1241)
- August 8 – Saint Dominic, founder of the Dominicans (d. 1221)
- Eustace the Monk, French pirate (d. 1217)
- Isabella of Hainault, queen of Philip II of France (d. 1190)
- Muqali, general of Genghis Khan
- Agnes I, Countess of Nevers
- Approximate date – Fibonacci (Leonardo Pisano Bigollo), Pisan mathematician (d. 1240/50)
- January 22 – Wang Chongyang, Chinese Daoist, co-founder of the Quanzhen School (b. 1113)
- April 23 – Minamoto no Tametomo, Japanese samurai, first known person to die by seppuku (b. 1139)
- November 18 – Albert I of Brandenburg (b. c. 1100)
- November 23 or November 28 – Owain Gwynedd, King of Gwynedd (b. c. 1100)
- December 29 – Thomas Becket, Archbishop of Canterbury (assassinated) (b. c. 1118)
- Al-Mustanjid, Abbasid Caliph in Baghdad
- Ruben II, Prince of Armenia (b. 1160)
- Mstislav II of Kiev
- Eliezer ben Nathan, Jewish poet, writer (b. 1090)
- Odo, Viscount of Porhoet, co-ruler of the duchy of Brittany
- Foster, R. F. (1989). The Oxford Illustrated History of Ireland. Oxford University Press.
- "Largest Cities Through History". About.com Geography.