Year 260 (CCLX) was a leap year starting on Sunday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Saecularis and Donatus (or, less frequently, year 1013 Ab urbe condita). The denomination 260 for this year has been used since the early medieval period, when the Anno Dominicalendar era became the prevalent method in Europe for naming years.
Events
By place
Roman Empire
Battle of Edessa: With a large army, said to number 70,000 men, Valerian attempts to drive the Persians back from Edessa. The Roman army is surrounded and most of its troops are killed or captured. Valerian is taken prisoner for the remainder of his life.
King Shapur I sends Valerian to Bishapur and uses the captured Roman army for engineering plans. They construct the Band-e Kaisar ("Bridge of Valerian").
Gallienus establishes himself at Mediolanum (modern Milan); he reorganizes the army, supported by elite cavalry, and dispatches troops to the Rhine frontier.
Postumus executes Saloninus and his adviser Silvanus after breaching the walls of Cologne. He is recognized as emperor and establishes his capital at Trier.
Emperor Cao Mao of Former Wei state attempts to lead a coup against the powerful regent Sima Zhao, but he himself is killed before it comes to a confrontation.
June 2 – Cao Mao is killed in a coup d'état against Sima Zhao. The 14-year-old Cao Huan becomes ruler of Former Wei, but the Sima clan controls the state.
Pope Dionysius convenes a synod at Rome to demand an explanation from bishop Dionysius of Alexandria, who has been charged with separating the members of the Trinity as three distinct deities.
