• In the Battle of the Masts, Muslim general Mu'awiyah crushes the Byzantine navy off the coast of Lycia, clearing the way for further Muslim encroachments on Byzantine territory in the eastern Mediterranean.
• The Korean kingdoms of Paekche and Koguryo band together to attack Silla, which is saved only by the timely intervention of the Tang emperor Gaozong.
• Oswiu, King of Northumbria defeats and slays Mercian king Penda in the Battle of Winwaed. The battle is lost for Penda because his ally King Cadfael ap Cynfeddw of Gwynedd chickens out at the last moment and refuses to fight, becoming known thereafter as Cadfael Cadomedd ("Cadfael the Battle-Shirker").
• The Croyland Chronicle, an important source for medieval English history, is begun at the Benedictine Abbey of Croyland, in Lincolnshire, England by a certain "Ingulf of Croyland," and will be added to on and off until 1486.

These people were born in 655:

• Leoduin, Bishop of Treves in Austrasia.

These people died in 655:

• Pope Martin I, in exile.
• Clovis II, king of the Franks, succeeded by his son Lothair III.
• Penda, King of Mercia, slain at the Battle of Winwaed, succeeded by his son Peada.

654 - 655 - 656

7th century