|1261 by topic|
|Birth and death categories|
|Births – Deaths|
|Establishments and disestablishments categories|
|Establishments – Disestablishments|
|Art and literature|
|1261 in poetry|
|Ab urbe condita||2014|
|Balinese saka calendar||1182–1183|
|English Regnal year||45 Hen. 3 – 46 Hen. 3|
|Chinese calendar||庚申年 (Metal Monkey)|
3957 or 3897
— to —
辛酉年 (Metal Rooster)
3958 or 3898
|- Vikram Samvat||1317–1318|
|- Shaka Samvat||1182–1183|
|- Kali Yuga||4361–4362|
|Japanese calendar||Bun'ō 2 / Kōchō 1|
|Minguo calendar||651 before ROC|
|Thai solar calendar||1803–1804|
1387 or 1006 or 234
— to —
1388 or 1007 or 235
- March 13 – Treaty of Nymphaeum: Emperor Michael VIII (Palaiologos) signs a trade and defense agreement with the Republic of Genoa, to counterweight the Venetian presence in the region. Genoa agrees to ally with the Empire of Nicaea, by providing a fleet of up to 50 galleys during the projected Nicaean siege of Constantinople, while 16 galleys are to be immediately sent against the Latin Empire.
- July – Michael VIII (Palaiologos) sends his general Alexios Strategopoulos with a small advance force of 800 soldiers, most of them Cumans, to keep watch on the Bulgarians and scout the defending positions of the Latin forces in the surroundings of Constantinople. When they reach the village of Selymbria, Strategopoulos is informed by local farmers that the entire Latin garrison and the Venetian fleet, are absent conducting a raid against the Nicaean island of Daphnousia. He decides not to lose such a golden opportunity and makes plans (without the consent of Michael) to retake the capital.
- July 25 – Reconquest of Constantinople: Alexios Strategopoulos and his men hide at a monastery near the city gates, before entering through a secret passage. After a short struggle, the guards who are completely taken by surprise are killed and the Venetian quarter is set ablaze. Panic spreads through the capital and Emperor Baldwin II rushes out to save his life, evacuating along with many other Latins with the help of the Venetian fleet. Baldwin manages to escape to the still Latin-held parts of Greece, but Constantinople is lost for good.
- August 15 – Michael VIII (Palaiologos) enters Constantinople in triumph and is crowned as emperor of the Byzantine Empire at the Hagia Sophia. To solidify his claim, the legitimate ruler, John IV (Laskaris), is blinded on Michael's orders on his 11th birthday. He banishes him to a monastery and marries his two sisters to lesser Latin and Bulgarian nobles in an attempt to wipe out the Laskarid Dynasty.
- Kublai Khan releases 75 Chinese merchants, who were captured along the border of the Mongol Empire. By doing this, Kublai hopes to bolster his popularity and depend on the cooperation of his Chinese subjects to ensure that his army receives more resources.
- June 13 – Al-Mustansir becomes the first Abbasid ruler in Cairo (after his escape during the Siege of Baghdad). He is sent with an army by Sultan Baibars I to recover Baghdad, but is killed in a Mongol ambush near Anbar (modern Iraq), on November 28. The Abbasid caliphs continue as religious figureheads for the Mamluks in Egypt until the 16th century.
- June 12 – King Henry III obtains a papal bull to absolve himself from his oath to maintain the Provisions of Oxford. He hires an army of 300 French knights as a bodyguard and takes up position in the Tower of London. He dismisses the baronial officials (led by Simon de Montfort) who wish the royal power to be modified by the principle of representation. This sets the stage for the Second Barons' War.
- August – Battle of Callann: Norman forces under John FitzThomas are defeated by a Gaelic army led by King Fínghin Mac Carthaigh. John FitzGerald is killed during the fighting.
- February – The Japanese Bun'ō era ends and the Kōchō era begins during the reign of the 11-year-old Emperor Kameyama (until 1264).
- The earliest extant Chinese illustration of "Pascal's Triangle" is from Yang Hui's (or Qianguang) book Xiangjie Jiuzhang Suanfa, published this year.
- May 25 – Pope Alexander IV dies after a pontificate of 6-years at Viterbo. He is succeeded by Urban IV as the 182nd pope of the Catholic Church.
- August 29 – Urban IV offers the crown of Sicily to Charles of Anjou, youngest son of King Louis VIII (the Lion), hoping to strengthen his position.
- Wurmsbach Abbey (located in Bollingen) is established by Count Rudolf V of Rapperswil in Switzerland.
- February 1 – Walter de Stapledon, bishop of Exeter (d. 1326)
- February 11 – Otto III, king of Hungary and Croatia (d. 1312)
- February 28 – Margaret of Scotland, queen of Norway (d. 1283)
- March 1 – Hugh le Despenser, English chief adviser (d. 1326)
- July 25 – Arthur II, Breton nobleman (House of Dreux) (d. 1312)
- October 9 – Denis I (the Poet King), king of Portugal (d. 1325)
- Abu Abdallah ibn al-Hakim, Andalusian vizier and poet (d. 1309)
- 'Ala' al-Dawla Simnani, Persian Sufi mystic and writer (d. 1336)
- Albertino Mussato, Italian statesman and chronicler (d. 1329)
- Constantine Palaiologos, Byzantine prince and general (d. 1306)
- Daniel of Moscow (Aleksandrovich), Russian prince (d. 1303)
- Danyi Chenpo Zangpo Pal, Tibetan religious leader (d. 1323)
- Elizabeth of Sicily, queen of Hungary (House of Anjou) (d. 1303)
- Konoe Iemoto, Japanese nobleman (kugyō) and regent (d. 1296)
- Pier Saccone Tarlati, Italian nobleman and condottiero (d. 1356)
- Władysław I Łokietek (Elbow-High), king of Poland (d. 1333)
- February 28 – Henry III (the Good), duke of Brabant (b. 1230)
- April 1 – Ahi Evren, Bektashi Sufi preacher and poet (b. 1169)
- May 25 – Alexander IV, pope of the Catholic Church (b. 1199)
- July 8 – Adolf IV, German nobleman (House of Schaumburg)
- July 25 – Nicephorus II of Constantinople, Byzantine patriarch
- August 24 – Ela of Salisbury, English noblewoman (b. 1187)
- September 18 – Konrad von Hochstaden, German archbishop
- October 27 – Sancho of Castile, Spanish archbishop (b. 1233)
- November 9 – Sanchia of Provence, German queen (b. 1225)
- November 26 – Hōjō Shigetoki, Japanese samurai (b. 1198)
- November 27 – Athanasius III of Alexandria, Egyptian pope
- November 28 – Al-Mustansir, Abbasid ruler (caliph) of Cairo
- Abu Bakr ibn Sayyid al-Nās, Andalusian theologian (b. 1200)
- An-Nasir Dawud, Ayyubid ruler (emir) of Damascus (b. 1206)
- Benedict II, Hungarian chancellor, governor and archbishop
- Bettisia Gozzadini, Italian noblewoman and jurist (b. 1209)
- Conrad I (the Pious), German nobleman and knight (b. 1186)
- John FitzThomas, Norman nobleman (House of Desmond)
- Plaisance of Antioch, queen consort of Cyprus (b. 1235)
- Qin Jiushao, Chinese mathematician and writer (b. 1202)
- Sayf al-Din al-Bakharzi, Persian poet and sheikh (b. 1190)
- Stephen of Bourbon, French Dominican preacher (b. 1180)
- Steven Runciman (1952). A History of The Crusades. Vol III: The Kingdom of Acre, p. 240. ISBN 978-0-241-29877-0.
- Bartusis, Mark C. (1997). The Late Byzantine Army: Arms and Society, 1204–1453, pp. 40–41. University of Pennsylvania Press. ISBN 0-8122-1620-2.
- Nicol, Donald M. (1993). The Last Centuries of Byzantium, 1261–1453, p. 35 (Second ed.). Cambridge: Cambridge University Press. ISBN 978-0-521-43991-6.
- Hackel, Sergei (2001). The Byzantine Saint, p. 71 (2001 ed.). St. Vladimir's Seminary Press. ISBN 0-88141-202-3.
- Rossabi, Morris (1988). Khubilai Khan: His Life and Times, p. 51. Los Angeles: University of California Press. ISBN 978-0-520-06740-0.
- Lock, Peter (2013). The Routledge Companion to the Crusades. Routledge. p. 112. ISBN 9781135131371.
- Williams, Hywel (2005). Cassell's Chronology of World History. London: Weidenfeld & Nicolson. pp. 144–146. ISBN 0-304-35730-8.
- BBC History, July 2011, p. 12.