Year 647 (DCXLVII) was a common year starting on Monday of the Julian calendar. The denomination 647 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.

• Arab–Byzantine War: An Arab army (20,000 men) under Abdullah ibn Sa'ad invades the Byzantine Exarchate of Africa. It conquers Tripolitania and the city of Sufetula, 150 miles (240 km) south of Carthage.
• Self-proclaimed emperor Gregory the Patrician is killed during the Arab invasion at Sufetula. Africa returns to imperial allegiance after his death, but the foundation of Byzantine rule is fatally undermined.

• Emperor Taizong of the Tang dynasty sends a Chinese mission to study Indian techniques of sugar manufacturing, at Bihar in the Ganges Valley.^[1]
• Taizong establishes a Chinese military government to pacify the former territory of Xueyantuo, which extends to the Altai Mountains in the west.
• Emperor Harsha, ruler of northern India, dies after a 41-year reign. His kingdom disintegrates into smaller states.
• Jindeok becomes queen of the Korean kingdom of Silla after the death of Queen Seondeok.^[2]

• A stone tower astronomical observatory (named Cheomseongdae) at Gyeongju is constructed in Silla (South Korea) around this time.

• Hilda of Whitby, age 33, is persuaded by Aidan, bishop of Lindisfarne, to enter the monastic life at Hartlepool Abbey (Northumbria).

• Al-Abbas ibn Ali, Muslim martyr (d. 680)
• Itzamnaaj B'alam II, ruler of Yaxchilan (d. 742)

• Æthelburh of Kent, queen of Northumbria
• Felix of Burgundy, bishop of Dunwich (or 648)
• Gao Shilian, chancellor of the Tang dynasty (b. 576)
• Gregory the Patrician, Exarch of Africa
• Harsha, emperor of Harsha (India)
• Li Baiyao, Chinese official and historian (b. 564)
• Seondeok, queen of Silla (Korea)^[2]
• Xiao Yu, prince of the Liang dynasty (b. 574)
• Yang Shidao, chancellor of the Tang dynasty