|Centuries:||6th century – 7th century – 8th century|
|Decades:||630s 640s 650s – 660s – 670s 680s 690s|
|Years:||661 662 663 – 664 – 665 666 667|
|664 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1417|
|Chinese calendar||癸亥年 (Water Pig)
3360 or 3300
— to —
甲子年 (Wood Rat)
3361 or 3301
|- Vikram Samvat||720–721|
|- Shaka Samvat||585–586|
|- Kali Yuga||3764–3765|
|Minguo calendar||1248 before ROC
|Seleucid era||975/976 AG|
|Thai solar calendar||1206–1207|
Year 664 (DCLXIV) was a leap year starting on Monday (link will display the full calendar) of the Julian calendar. The denomination 664 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.
- Plague devastates Gwynedd (Wales) and depopulates the southern coasts of England. King Cadafael Cadomedd dies and is succeeded by Cadwaladr who reasserts himself in his kingdom by sending his son Ivor from Brittany to be regent.
- King Ealdwulf succeeds Æthelwald as king of East Anglia. He becomes the last ruler that Bede, a Northumbrian monk, knows about.During his reign a great plague sweeps across the Anglo-Saxon kingdoms.
- July 14 – King Eorcenberht of Kent dies after a 24-year reign and is succeeded by his son Ecgberht. Queen Seaxburh becomes regent, ruling Kent until Ecgberht comes of age.
- King Swithelm of Essex dies after a 4-year reign. He is succeeded by his cousins Sighere and Sæbbi (approximate date).
- Muslim Conquest: Arab forces under Al-Muhallab ibn Abi Suffrah begin launching raids from Persia, striking at Multan in the southern Punjab (modern Pakistan). Muslims conquer the city of Kabul, invading from eastern Afghanistan.
- Synod of Whitby: King Oswiu of Northumbria calls for a meeting at Whitby Abbey to settle the church practices in his kingdom—those of the Celtic Church (of Wales, Scotland and the north of England - preached by Irish missionaries) or the Roman Church (of the south of England). The matters discussed include how to calculate the date of Easter. It is decided to follow the practice of Rome. As a result, many Irish clergy leave Northumbria and return to Ireland.
- January 6 – 'Amr ibn al-'As, Arab general
- February 5 – Xuanzang, Chinese Buddhist monk and traveler
- July 14 – Eorcenberht, king of Kent
- October 21 – Tuda, bishop of Lindisfarne
- October 26 – Cedd, bishop of London
- Æthelwald, king of East Anglia (approximate date)
- Alhfrith, king of Deira (approximate date)
- Cadafael Cadomedd, king of Gwynedd (Wales)
- Deusdedit of Canterbury, archbishop of Canterbury
- Swithelm, king of Essex (approximate date)
- Yorke, "King of Kingdoms", p. 63
- Roberts, J: "History of the World.". Penguin, 1994.