|Centuries:||2nd century – 3rd century – 4th century|
|Decades:||230s 240s 250s – 260s – 270s 280s 290s|
|Years:||262 263 264 – 265 – 266 267 268|
|265 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1018|
|Chinese calendar||甲申年 (Wood Monkey)
2961 or 2901
— to —
乙酉年 (Wood Rooster)
2962 or 2902
|Coptic calendar||−19 – −18|
|- Vikram Samvat||321–322|
|- Shaka Samvat||187–188|
|- Kali Yuga||3366–3367|
|Iranian calendar||357 BP – 356 BP|
|Islamic calendar||368 BH – 367 BH|
|Minguo calendar||1647 before ROC
|Seleucid era||576/577 AG|
|Thai solar calendar||807–808|
Year 265 (CCLXV) was a common 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 Valerianus and Lucillus (or, less frequently, year 1018 Ab urbe condita). The denomination 265 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 Gallienus tries twice to crush the usurper Postumus, but on the first occasion Aureolus, commander of the elite cavalry, carelessly lets him escape. The second time, Gallienus sustains an arrow wound and has to break off his siege of a Gallic town where Postumus has holed up. He makes no other serious attempt to overcome his rival, devotes his attention to the political and military problems in the Danube and eastern parts of the Roman Empire.
- Postumus makes no move to march on Rome and claim his territory south of Gaul.
- Gallienus gives the order to fortify Milan and Verona.
- Gallienus repels the invasion of the Goths in the Balkans.
- A general of Gallienus' army, Victorinus, defects to Postumus.
- Three Kingdoms: Sima Yan forces emperor Cao Huan to abdicate the throne to him, ending the Kingdom of Wei in China.
- Jin Wudi becomes ruler of part of China, beginning the Jin Dynasty. He establishes his capital at Luoyang and gives princes of his uncles, cousins, brothers, and sons, independent military commands in the Chinese Empire.
- Ma Jun, Chinese engineer and inventor of the south-pointing chariot
- Empress Zhu, wife of Sun Xiu of Eastern Wu during the Three Kingdoms
- Sima Zhao, son of Sima Yi, younger brother of Sima Shi and general of Wei (b. 211)