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Year 657 (DCLVII) was a common year starting on Sunday (link will display the full calendar) of the Julian calendar. The denomination 657 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.
|Ab urbe condita||1410|
|Balinese saka calendar||578–579|
|Chinese calendar||丙辰年 (Fire Dragon)|
3353 or 3293
— to —
丁巳年 (Fire Snake)
3354 or 3294
|- Vikram Samvat||713–714|
|- Shaka Samvat||578–579|
|- Kali Yuga||3757–3758|
|Minguo calendar||1255 before ROC|
|Seleucid era||968/969 AG|
|Thai solar calendar||1199–1200|
783 or 402 or −370
— to —
784 or 403 or −369
- Grimoald the Elder, mayor of the palace of Austrasia, is deposed by Clovis II, king of Neustria. Clovis also captures Grimoald's son Childebert the Adopted, executing them both.
- Clovis II dies and is succeeded by his eldest son Chlothar III, age 5, who becomes king of Neustria and Burgundy, under the regency of his mother Balthild.
- Battle of Siffin: Muslim forces under Ali ibn Abi-Talib fight an inconclusive battle against Muawiyah ibn Abu Sufyan, on the banks of the Euphrates, near Raqqa (Syria).
- Tang campaigns against the Western Turks: Emperor Gao Zong dispatches a military campaign led by Su Dingfang. He annexes the Western Turkic Khaganate.
- Gao Zong commissions the pharmacology publication of an official materia medica, documenting the use of 833 different substances for medicinal purposes.
- In the course of the Second Tikal-Calakmul War, the Snake Lord (Yuknoom Ch'een II) makes a direct attack against Tikal itself, driving out its new ruler Nuun Ujol Chaak, and establishing Calakmul as the regional superpower. B'alaj Chan K'awiil, the one time heir apparent to rule Tikal, swears his allegiance to the new overlord.
- June 2 – Pope Eugene I
- November 12 – Livinus, Irish apostle
- Ammar ibn Yasir, companion of Muhammad and Ali ibn Abi Talib (b. 570)
- Childebert the Adopted, king (usurper) of Austrasia
- Clovis II, king of Neustria and Burgundy (or 658)
- Grimoald the Elder, Mayor of the Palace (b. 616)
- Talorgan I, king of the Picts
- "Saint Hilda of Whitby | English abbess". Encyclopedia Britannica. Retrieved February 14, 2020.