Year 1177 (MCLXXVII) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar.
January – Eystein Meyla, leader of the Birkebeiner in Norway, is killed. Sverre Sigurdson (Later, King Sverre I, of Norway) becomes the new leader.
January 13 - Leopold V becomes Duke of Austria.
March – Treaty of Venice: Frederick I Barbarossa acknowledges Alexander III as Pope.
August 1 – Holy Roman Empire renounces any claims on the territory of Rome.
September 27 – Pope Alexander III sends a letter to Prester John, believing he is real.
November 25 – Battle of Montgisard: Baldwin IV of Jerusalem and Raynald of Chatillon defeat Saladin.
During the third year of the Angen era in Japan, a fire devastates Kyoto.
During the winter, the Estonians attack Pskov.
Casimir II overthrows his brother Mieszko III the Old to become High Duke of Poland.
The Cham sack the Khmer capital of Angkor Wat.
Moscow is burned down and its inhabitants are killed.
A civil war breaks out in the Republic of Florence between the Uberti family and their consular opponent.
Puigcerdà is founded by Alfonso II of Aragon.
Byland Abbey is established on its final site in Yorkshire, England, by the Cistercians.
Abbas Benedictus becomes abbot of Peterborough in England.
Roger de Moulins becomes Grand Master of the Knights Hospitaller.
Possible date – Richard FitzNeal begins to write his treatise Dialogus de Scaccario ("Dialogue concerning the Exchequer") in England.
February/March – Philip of Swabia, rival of Otto IV, Holy Roman Emperor (d. 1208)
August – Baldwin V, King of Jerusalem (d. 1186)
January 13 – Henry II, Duke of Austria (b. 1107)
January – Eystein Meyla, leader of the Birkebeiner in Norway. (b. 1157)
June – William of Montferrat, Count of Jaffa and Ascalon, father of Baldwin V of Jerusalem (b. early 1140s)
probable – Hugh Bigod, 1st Earl of Norfolk (b. 1095)
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