|318 by topic|
|Ab urbe condita||1071|
|Balinese saka calendar||239–240|
|Chinese calendar||丁丑年 (Fire Ox)|
3014 or 2954
— to —
戊寅年 (Earth Tiger)
3015 or 2955
|- Vikram Samvat||374–375|
|- Shaka Samvat||239–240|
|- Kali Yuga||3418–3419|
|Iranian calendar||304 BP – 303 BP|
|Islamic calendar||313 BH – 312 BH|
|Minguo calendar||1594 before ROC|
|Seleucid era||629/630 AG|
|Thai solar calendar||860–861|
444 or 63 or −709
— to —
445 or 64 or −708
Year 318 (CCCXVIII) was a common year starting on Wednesday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Licinianus and Crispus (or, less frequently, year 1071 Ab urbe condita). The denomination 318 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 gives the ancient Roman town Drepana (Asia Minor) the name Helenopolis, after his mother Helena, and builds a church in honour of the martyr St. Lucian.
- Constantine the Great is given the title Brittanicus Maximus, for successful engagements in Britain.
- The Chinese Empire loses its territories to the north of the Yangtze River, to the benefit of the Xiongnu and the Xianbei. The Former Zhao state is proclaimed; Liu Can and the state ruling family at Pingyang is executed in a coup d'état by Jin Zhun, who is in turn overthrown by Shi Le and Liu Yao.
- Liu Yao becomes the new emperor of Han Zhao and moves his capital to Chang'an.
- Gregory the Illuminator appoints his son Aristax as successor in the patriarchate of Armenia.
- February 7 – Min of Jin, Chinese emperor (b. 300)
- August 31 – Liu Cong, Chinese emperor
- Fan Changsheng, Chinese religious leader
- Jin Zhun, Chinese official and chancellor
- Liu Can (or Shiguang), Chinese emperor
- Liu Kun, Chinese general and poet (b. 270)
- Theodota of Philippi, Greek harlot and martyr