Year 1221 (MCCXXI) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.
January – The Mongol army under Jochi captures the city of Gurganj (modern-day Konye-Urgench in Turkmenistan) and massacres the inhabitants, reported by contemporary scholars as being over a million.February – The oasis city of Merv on the Silk Road is sacked by the Mongols under Tolui at the orders of Genghis Khan. Contemporary scholars report over a million people are systematically killed in a genocide.May 13 – Emperor Juntoku is forced to abdicate and is briefly succeeded by his 2-year-old son Emperor Chūkyō on the throne of Japan. Ex-Emperor Go-Toba leads the unsuccessful Jōkyū War against the Kamakura shogunate.June 16 – The Jews of Erfurt, Germany are massacred al Kiddush Hashem. This day was observed as a fast day for many years.The Jews were falsely accused of a ritual murder. A crowd stormed the synagogue where the Jews had gathered. As usual the threat was baptism or death. The Jewish quarter including the synagogue was razed, many Jews were tortured and killed. Among the martyrs were Shem Tov ha-Levi and Rabbi and Mrs. Shmuel Kalonymos, Hy"d.
July 29 – 10-year-old Emperor Go-Horikawa ascends to the Chrysanthemum Throne of Japan.Mid-December – John III Doukas Vatatzes becomes Byzantine Emperor (in the Empire of Nicaea).A large and highly efficient Mongol army, dispatched under Subutai by Genghis Khan to Georgia, defeats two Georgian armies around Tbilisi, but lacks the will or equipment to besiege the city.Genghis Khan enters the Indus Valley in modern-day Pakistan.Majd al-Mulk al-Muzaffar, the grand vizier of Greater Khorasan, is killed in a genocide by the Mongol invaders.The Maya of the Yucatán revolt against the rulers of Chichen Itza.Sultan al-Kamil, son of al-Adil ("Saphadin") who was a brother of Saladin, offers Jerusalem to the Crusaders for ten years in return for Damietta, which the Crusaders eventually give up in exchange for a safe retreat from the Nile Delta.The city of Nizhny Novgorod in Russia is founded.October 9 – Salimbene di Adam, Italian chroniclerNovember 23 – King Alfonso X of Castile (d. 1284)Bonaventure, Italian theologian and saint (d. 1274)Boleslaus the Pious, Duke of Greater Poland (d. 1279)August 6 – Saint Dominic, Spanish founder of the Dominicans (b. 1170)October 4 – William IV Talvas, Count of Ponthieu (b. 1179)October 21 – Alix of Thouars, Duchess of Brittany (b. 1201)Roger Bigod, 2nd Earl of NorfolkMutukan, 1st Son of Chagatai Khan 