The 1230s was a decade of the Julian Calendar which began on January 1, 1230, and ended on December 31, 1239.
- Sundiata starts to rule in Mali (approximate date).
- In the West African village of Siby, Sundiata Keita, founder of the Mali Empire, forces the Malinkés to bind themselves to each other by oath.
- August 10–12 – Battle of Yassıçemen: Sultan Kayqubad I of Rum defeats Shah Jala9 7 1 9 ad-Din of Persia, ending the Khwarazmian Dynasty.
- The Sena Dynasty of Bengal falls.
- March 9 – Battle of Klokotnitsa: Bulgarian tsar Ivan Asen II defeats the Emperor of Thessalonica Theodore Komnenos Doukas. In the aftermath, Bulgaria quickly extends its control over most of Theodore's domains in Thrace, Macedonia, and Albania. The Latin Duchy of Philippopolis and the independent principality of Alexius Slav are also captured, and annexed into Bulgaria.
- Iberian Peninsula – Battle of Alange: Alfonso IX defeats Ibn Hud al-Yamani (known as Almogàver by the Christians). This success opens the road to Badajoz to the Leonese troops. The Portuguese king Sancho II continues his offensive southward, and takes Beja, Juromenha, Serpa and Moura.
- September 24 – The Kingdoms of León and Galicia unite with the Kingdoms of Castile and Toledo, under Ferdinand III.
- The Teutonic Knights are invited into Prussia, to forcibly convert the Prussians and Yatvags to Christianity.
- April 9 – After a bizarre weather phenomena of yellowish clouds and dust chokes the air around Hangzhou, Song Dynasty, China, obscuring the sky and sun, a fire breaks out at night in the southeast of the city, which continues into the next day. Fighting the flames is difficult due to limited visibility. When the fires are extinguished, it is discovered that an entire district of some 10,000 houses in the southeast of the city were consumed by the flames.
- Mongol troops cross the Yalu River into Korea, then under the Goryeo Kingdom.
- Italy: Emperor Frederick II promulgates the Constitutions of Melfi (also known as Liber Augustalis), a collection of laws for Sicily, as well as the edict of Salerno, regulating the exercise of medicine and separating the professions of physician and apothecary.
- Llywelyn the Great launches a campaign against the Norman lordships in Wales.
- Spain: The Castillans reconquer the city of Quesada.
- University of Cambridge granted a Royal Charter by King Henry III.
- The Almohad army besieges Ceuta, where Abu Musa, the rebellious brother of the caliph, has received shelter and the support of the population. The Genoese rent a part of their fleet to the rebels, who successfully resist the forces of the caliph. The consequences of this revolt are threefold: the city becomes de facto independent from the Almohads, but its reliance on the Italian maritime powers increases, and the trans-Saharan trade routes begin to shift eastward, due to the local turmoil.
- The first edition of Tripitaka Koreana is destroyed by Mongol invaders.
- April 8 – The Jin Dynasty in China defends their capital against the Mongol siege of Kaifeng, during the Mongol–Jin War. The battle involves the use of rockets.
- June 15 – Battle of Agridi: Henry I of Cyprus defeats the armies of Frederick II.
- July 16 – Muhammad Ibn Yusuf Ibn Nasr is elected ruler of Arjona, Spain, by the local mosque. He rebels against the independent ruler of al-Andalus, Ibn Hud al-Yadami, and takes control of the city. This is the foundation of the Nasrid Dynasty.
- Italy: Pope Gregory IX, driven from Rome by a revolt, takes refuge at Anagni.
- Holy Roman Emperor Frederick II promulgates the Statutum in favorem principum.
- The northern French city of Troyes issues its first recorded life annuities, confirming the trend of consolidation of local public debts initiated in 1218, by the neighboring city of Reims.
- May 30 – Anthony of Padua is canonized by Pope Gregory IX at Spoleto, less than a year after his death; he becomes the patron saint of lost items.
- February 26 – Mongol–Jin War: The Mongols capture Kaifeng, the capital of the Jin Dynasty, after besieging it for months.
- December – The Mongol siege of Caizhou begins.
- Winter – Spain: after the loss of Trujillo and Úbeda, Ibn Hud al-Yamadi has to request a truce from the king of Castile, Ferdinand III.
- The Castilian troops besiege the Muslim-held city of Peniscola.
- The rebellious city of San Severo is destroyed by Frederick II, Holy Roman Emperor.
- Elburg and Gendt get their city rights.
- Amadeus IV becomes count of Savoy.
- Pope Gregory IX forbids Jews to employ Christian servants.
- The Manden region rises against the Kaniaga Kingdom. This is the beginning of a process that will lead to the rise of the Mali Empire.
- February 9 – Mongol conquest of the Jin dynasty: In the Siege of Caizhou, Song Dynasty Chinese and Mongolian armies occupy the Jurchen capital at Caizhou, and Emperor Aizong of Jin commits suicide, marking the collapse of the Jin Dynasty.
- Upon the death of Knut Långe, the deposed Erik Eriksson returns as king of Sweden, possibly after a small war between the two of them. It is also possible that Knut dies of natural causes, and Erik peacefully then returns as king.
- Pope Gregory IX calls for a crusade against Bosnia, and replaces the Bogumil Bosnian Bishop with a Catholic Dominican German, Johann.
- King Andrew II of Hungary proclaims herzeg Coloman as Ban of Bosnia, who passes it on to Prijezda, a cousin of Ban Matej Ninoslav (1234 to 1239), despite Matej being the legitimate Ban of Bosnia.
- Sancho II of Portugal conquers the cities of Aljustrel and Mértola from the Muslims.
- Saint Dominic is canonized.
- Pope Gregory IX releases the Nova Compilatio Decretalium or Decretales Gregorii IX.
- Connacht in Ireland is finally conquered by the Hiberno-Norman Richard Mór de Burgh; Felim Ua Conchobair is expelled.
- A general inquisition begins in France.
- The Byzantine emperor John III Doukas Vatatzes and the Bulgarian tsar Ivan Asen II besiege Constantinople, in an attempt to take it from its Latin rulers, John of Brienne and Baldwin II. Angelo Sanudo successfully negotiates a two-year truce.
- Elizabeth of Hungary (d. 1231) is canonized, by Pope Gregory IX.
- A Chinese text of this year records that Hangzhou City, the capital of the Song Dynasty, held various social clubs that included a West Lake Poetry Club, the Buddhist Tea Society, the Physical Fitness Club, the Anglers' Club, the Occult Club, the Young Girls' Chorus, the Exotic Foods Club, the Plants and Fruits Club, the Antique Collectors' Club, the Horse-Lovers' Club, and the Refined Music Society.
- Probable date – The Lancaster Royal Grammar School is founded in England.
- Approximate date – Battle of Kirina: Mandinka prince Sundiata Keita defeats Sosso king Soumaoro Kanté, beginning the Mali Empire. By tradition, the Manden Charter, a constitution, is proclaimed in Kouroukan Fouga.
- May 1 – Razia Sultana is the designated successor of her father, to the Delhi Sultanate.
- Only four of 58 districts in Sichuan, China, are captured from the Southern Song by the Mongols, under Ögedei Khan.
- Kalinga Magha, founder of the Aryacakravarti Dynasty, is expelled from Polonnaruwa to Jaffna, the capital of the Jaffna Kingdom.
- January 14 – Henry III of England marries Eleanor of Provence.
- June 29 – Córdoba, Andalusia, is taken by Castilian troops from the emir Ibn Hud, as part of the Reconquista of the Iberian Peninsula. The Great Mosque here becomes wholly a Roman Catholic cathedral.
- September 22 – Battle of Saule: The Lithuanians and Semigallians defeat the Livonian Brothers of the Sword.
- Volga Bulgaria is conquered by the Mongol Batu Khan.
- A tournament at Tickhill in England turns into a battle between northerners and southerners, but peace is restored by the papal legate.
- May 6 – Roger of Wendover, Benedictine monk and chronicler of St. Albans Abbey dies. His chronicle is continued by Matthew Paris.
- A drought causes the harvest to fail, and leads to one of the great famines of the century in Europe.
- Thomas II of Savoy becomes count of Flanders.
- Elbing is founded in the State of the Teutonic Order (today Elbląg, Poland).
- After turning aside south for 15 years to invade the Caucasus, Asia Minor and Persia, Batu Khan (with representatives of all four khanates leading 150,000 Mongol, Turkish and Persian troops into Europe) resumes the European invasion, with the resumption of the Mongol invasion of Rus' foreshadowed thereby.
- December 21 – Mongol invasion of Rus': Ryazan is sacked.
- Gualdo Tadino, Italy, is destroyed by fire.
- The County of Artois is founded in France.
- Baldwin II becomes Latin Emperor of Constantinople.
- Conrad IV of Germany becomes King of Germany.
- Livonian Crusade: After their defeat in the Battle of Saule, the Livonian Brothers of the Sword are absorbed into the Teutonic Order, as the autonomous Livonian Order. An Estonian rebellion begins on Saaremaa Island.
- Battle of Cortenuova: Frederick II, Holy Roman Emperor defeats the Lombard League.
- A major fire destroys some 30,000 dwellings in the Chinese capital city of Hangzhou.
- March 4 – Mongol invasion of Rus – Battle of the Sit River: The Mongol Hordes of Batu Khan defeat the Rus', under Yuri Vsevolodovich of Vladimir-Suzdal.
- August 21 – Battle of Örlygsstaðir: Sighvatr Sturluson and Sturla Sighvatsson are defeated by Kolbeinn ungi Arnórsson and Gissur Þorvaldsson, for control of Iceland.
- September 28 – James I of Aragon captures the city of Valencia from the Moors, who retreat to Granada.
- The seat of the Patriarch of Aquileia is transferred to Udine.
- Simon de Montfort marries Eleanor, sister of Henry III of England.
- The Livonian Order gives Northern Estonia back to Denmark, with the Treaty of Stensby.
- The Mongols seize Moscow, at the time a small town.
- Peterborough Cathedral is consecrated.
- The founder of the Nasrid Dynasty, Muhammad I of Granada, begins Alhambra Complex on the site of a pre-Islamic fortress.
- Thowadra Monastery is founded in Bhutan.
- Communal uprisings in Santiago de Compostela against the archbishop.
- March 20 – Pope Gregory IX excommunicates Frederick II, Holy Roman Emperor.
- November – The Pope grants the status of Crusade, to the king of Castile's ongoing invasion of the Muslim kingdom of Murcia.
- Frederick II, Holy Roman Emperor conducts the Siege of Faenza.
- The main tower of Lincoln Cathedral in England collapses.
- Netley Abbey is founded in England.
- The Mongol invasion of Rus is in progress, bringing with it a pandemic of rinderpest.
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