|Centuries:||3rd century – 4th century – 5th century|
|Decades:||270s 280s 290s – 300s – 310s 320s 330s|
|Years:||305 306 307 – 308 – 309 310 311|
|308 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1061|
|Bahá'í calendar||−1536 – −1535|
|English Regnal year||N/A|
|Chinese calendar||丁卯年 (Fire Rabbit)
3004 or 2944
— to —
戊辰年 (Earth Dragon)
3005 or 2945
|- Vikram Samvat||364–365|
|- Shaka Samvat||230–231|
|- Kali Yuga||3409–3410|
|Igbo calendar||−692 – −691|
|Iranian calendar||314 BP – 313 BP|
|Islamic calendar||324 BH – 323 BH|
|Minguo calendar||1604 before ROC
|Thai solar calendar||851|
|Wikimedia Commons has media related to 308.|
Year 308 (CCCVIII) was a leap year starting on Thursday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Valerius and Valerius (or, less frequently, year 1061 Ab urbe condita). The denomination 308 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.
- April – Roman usurper Maxentius banishes his father, Maximian, who flees to the court of Constantine the Great in Augusta Treverorum (modern Trier).
- November 11 – The Congress of Carnuntum: Attempting to keep peace within the Roman Empire, the leaders of the Tetrarchy declare Maxentius a public enemy and Licinius is proclaimed Augustus, while rival contender Constantine I is declared Caesar of Britain and Gaul.
- Under Constantine I, the Romans defeat the Germans along the Rhine frontier.
- Domitius Alexander is acclaimed emperor (against Maxentius) in Carthage, the African provinces come under his rule. This is a dangerous situation, because Rome depends on the African grain supply.
- The Basilica of Maxentius is constructed, the largest building in the Roman Forum.