Year 1172 (MCLXXII) was a leap year starting on Saturday (link will display the full calendar) of the Julian calendar.
April/May – Béla returns to Hungary where he is acclaimed king.
Richard Lionheart becomes Duke of Aquitaine (later King Richard I of England).
Henry II of England and Humbert III, Count of Savoy agree to wed their respective heirs, John of England and Alicia. The alliance never occurs because Henry's elder heir, Henry the Young King, becomes jealous over the castles which the elder Henry promises to the couple and stages a rebellion which will take the elder Henry two years to put down. By that point, Alicia has died.
Alberto di Morra is sent by Pope Alexander III to the Council of Avranches, where Henry II of England is absolved of the sin of murder in the matter of the assassination of Thomas Becket.
The Synod of Cashel ends the Celtic Christian system and brings them under the Pope.
A Muslim rebellion is quelled at Prades, this event marks the end of the pacification of the lands recently conquered by the Catalans.
According to the annals of the Worcester Priory, "nothing memorable" happens in this year.
July – Baldwin I of Constantinople (d. 1205)
date unknown
Ranulph de Blondeville, 4th Earl of Chester (d. 1232)
Isabel de Clare, 4th Countess of Pembroke (d. 1220)
Louis I, Count of Blois (d. 1205)
Fujiwara Moroie, last of the Japanese Fujiwara Regents (d. 1238)
probable
Isabella of Jerusalem, Queen of Jerusalem 1190/1192–1205 (d. 1205)
March 4 – King Stephen III of Hungary (b. 1147)
December 23 – Ugo Ventimiglia, cardinal
date unknown
Il-Arslan, Khwarazm Shah
Douce II, Countess of Provence (b. 1165)
Acharya Hemachandra, Indian mathematician, philosopher and historian (b. 1089)
William III, Count of Ponthieu (b. c. 1095)
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