|Centuries:||3rd century – 4th century – 5th century|
|Decades:||310s 320s 330s – 340s – 350s 360s 370s|
|Years:||340 341 342 – 343 – 344 345 346|
|343 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||1096|
|Chinese calendar||壬寅年 (Water Tiger)
3039 or 2979
— to —
癸卯年 (Water Rabbit)
3040 or 2980
|- Vikram Samvat||399–400|
|- Shaka Samvat||265–266|
|- Kali Yuga||3444–3445|
|Iranian calendar||279 BP – 278 BP|
|Islamic calendar||288 BH – 287 BH|
|Minguo calendar||1569 before ROC
|Seleucid era||654/655 AG|
|Thai solar calendar||885–886|
|Wikimedia Commons has media related to 343.|
Year 343 (CCCXLIII) 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 Memmius and Romulus (or, less frequently, year 1096 Ab urbe condita). The denomination 343 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.
- The Western Roman Emperor Constans I is in Britain, possibly in a military campaign against the Picts and Scots.
- The Eastern Roman Emperor Constantius II campaigns in Adiabene, a vassal kingdom of Armenia (Persian Empire).
- Pope Julius I tries to unite the Western bishops against Arianism by convoking the Council of Sardica (later Sofia), which acknowledges the pope's supreme authority and grants him the right to judge cases involving the legal possession of episcopal sees, but only Western and Egyptian bishops attend, and Arianism remains strong.
- Fu Deng, emperor of the Di state Former Qin (d. 394)
- Jin Mudi, emperor of the Eastern Jin Dynasty (d. 363)
- Xiaoyi, empress dowager of the Liu Song Dynasty (d. 423)
- Xie Xuan, general of the Jin Dynasty (d. 388)
The number of firefighters that died on 9/11/2001