|Centuries:||3rd century – 4th century – 5th century|
|Decades:||300s 310s 320s – 330s – 340s 350s 360s|
|Years:||328 329 330 – 331 – 332 333 334|
|331 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1084|
|Bahá'í calendar||−1513 – −1512|
|English Regnal year||N/A|
|Chinese calendar||庚寅年 (Metal Tiger)
3027 or 2967
— to —
辛卯年 (Metal Rabbit)
3028 or 2968
|- Vikram Samvat||387–388|
|- Shaka Samvat||253–254|
|- Kali Yuga||3432–3433|
|Igbo calendar||−669 – −668|
|Iranian calendar||291 BP – 290 BP|
|Islamic calendar||300 BH – 299 BH|
|Minguo calendar||1581 before ROC
|Thai solar calendar||874|
|Wikimedia Commons has media related to 331.|
Year 331 (CCCXXXI) was a common year starting on Friday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Bassus and Ablabius (or, less frequently, year 1084 Ab urbe condita). The denomination 331 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 Constantine the Great vigorously promotes Christianity, confiscating the property and valuables of a number of pagan temples throughout the Roman Empire.
- Constantine I dedicated the Church of the Holy Apostles in Constantinople.
- Constantine I promulgates a law against divorce.
Arts and sciences
- Eusebius of Caesarea writes the Onomasticon.
- Jovian, Roman Emperor (d. 364)
- Julian the Apostate, Roman Emperor (d. 363)
- Yao Chang, emperor of the Qiang state Later Qin (d. 394)