Year 637 (DCXXXVII) was a common year starting on Wednesday (link will display the full calendar) of the Julian calendar. The denomination 637 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
|637 by topic|
|Ab urbe condita||1390|
|Balinese saka calendar||558–559|
|Chinese calendar||丙申年 (Fire Monkey)|
3333 or 3273
— to —
丁酉年 (Fire Rooster)
3334 or 3274
|- Vikram Samvat||693–694|
|- Shaka Samvat||558–559|
|- Kali Yuga||3737–3738|
|Minguo calendar||1275 before ROC|
|Seleucid era||948/949 AG|
|Thai solar calendar||1179–1180|
763 or 382 or −390
— to —
764 or 383 or −389
- June 24 – Battle of Mag Rath: King Oswald of Northumbria sends troops to Ireland, to assist Domnall Brecc King of Dál Riata in his alliance with King Congal Cáech of Ulaid against Domnall mac Áedo High King of Ireland, during the Irish dynastic wars. Domnall Brecc, Congal and their forces are defeated near Moira. At the Mull of Kintyre (southwest Scotland), Domnall mac Áedo's fleet destroys Domnall Brecc's naval force of Dál Riata.
- March – Siege of Ctesiphon: The Rashidun army (15,000 men) under Saʿd ibn Abi Waqqas occupies the Persian capital of Ctesiphon, after a two-month siege. King Yazdegerd III flees with the imperial treasure eastward into Media. Muslim forces conquer the Persian provinces as far as Khuzestan (modern Iran).
- Battle of Jalula: Muslim Arabs defeat the Persian forces (20,000 men) under Farrukhzad at the Diyala River. The cities Tikrit and Mosul are captured, completing the conquest of Mesopotamia. The region west of the Zagros Mountains is annexed by the Rashidun Caliphate.
- April – Siege of Jerusalem: The Rashidun army (20,000 men), led by 'Amr ibn al-'As, conquers Jerusalem after a six-month siege. The Byzantine garrison surrenders to Caliph Umar I, who is invited by Sophronius, patriarch of Jerusalem, to pray in the Church of the Holy Sepulchre. Umar declines, fearing that accepting the invitation might endanger the church's status, and turn the Christian holy site into a mosque.
- Battle of Hazir: Muslim Arab forces (17,000 men) under Khalid ibn al-Walid defeat the Byzantine army near Qinnasrin (Northern Syria). The cities of Beirut and Tyre are captured by Yazid ibn Abi Sufyan after a short siege.
- October – Siege of Aleppo: Muslim Arabs under Khalid ibn al-Walid conquer the Byzantine stronghold Aleppo; the large walled city surrenders after a four-month siege. A column of troops under Malik al-Ashtar is sent to take Azaz.
- Battle of the Iron Bridge: Rashidun forces under Khalid ibn al-Walid defeat the Byzantine army and Christian Arabs near Antioch, at the Orontes River. It marks the complete annexation of Syria into the Rashidun Caliphate.
- Chang'an, capital of the Tang Dynasty (China), becomes the largest city of the world, taking the lead from Ctesiphon, capital of Persia.
- Queen Seondeok of Silla (Korea) builds near Gyeongju an astronomical observatory (Cheomseongdae), one of the oldest in East Asia.
- King Songtsän Gampo builds the first palace on the site of the Potala Palace in Lhasa (Tibet).
- Andreas of Caesarea, bishop and writer (b. 563)
- Congal Cáech, high king of Dál nAraidi (Ireland)
- John Athalarichos, illegitimate son of Heraclius
- Maria al-Qibtiyya, concubine of Muhammad
- Mo Chua, Irish bishop and founder of Balla
- Mo Chutu, Irish abbot and founder of Lismore Abbey
- Rostam Farrokhzād, Persian general (or 636)
- Wen Yanbo, chancellor of the Tang Dynasty (b. 575)