|Centuries:||2nd century – 3rd century – 4th century|
|Decades:||220s 230s 240s – 250s – 260s 270s 280s|
|Years:||256 257 258 – 259 – 260 261 262|
|259 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1012|
|Chinese calendar||戊寅年 (Earth Tiger)
2955 or 2895
— to —
己卯年 (Earth Rabbit)
2956 or 2896
|Coptic calendar||−25 – −24|
|- Vikram Samvat||315–316|
|- Shaka Samvat||181–182|
|- Kali Yuga||3360–3361|
|Iranian calendar||363 BP – 362 BP|
|Islamic calendar||374 BH – 373 BH|
|Minguo calendar||1653 before ROC
|Seleucid era||570/571 AG|
|Thai solar calendar||801–802|
Year 259 (CCLIX) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Aemilianus and Bassus (or, less frequently, year 1012 Ab urbe condita). The denomination 259 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.
- Emperor Valerian leads an army (70,000 men) to relieve Edessa, besieged by the forces of king Shapur I. An outbreak of a plague kills many legionaries, weakening the Roman position in Syria.
- Battle of Mediolanum: A Germanic confederation, the Alamanni (300,000 warriors), who crossed the Alps are defeated by Roman legions under Gallienus near Mediolanum (modern Milan).
- Postumus revolts against Gallienus in Gaul. The western provinces of Britain and Spain join his independent realm—which is called in modern times the Gallic Empire.
- Postumus, governor of Gaul, declares himself Emperor and continues to rule the Gallic Empire until 269 when he was killed by his soldiers.
- The Roman fort of Wiesbaden (Germany) is captured by the Alamanni (possibly 260).
- The Franks, who invaded the Roman Empire near Cologne in 257, reach Tarraco in Hispania.
- Mesopotamia: Odaenathus, the ruler of the kingdom of Palmyra, sacks the city of Nehardea, destroying its great yeshiva.
- Jin Huidi, emperor of the Jin Dynasty (d. 307)
- Tao Kan, general of the Jin Dynasty (d. 334)
- Yang Zhi, empress of the Jin Dynasty (d. 292)