|Centuries:||2nd century – 3rd century – 4th century|
|Decades:||210s 220s 230s – 240s – 250s 260s 270s|
|Years:||240 241 242 – 243 – 244 245 246|
|243 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||996|
|Chinese calendar||壬戌年 (Water Dog)
2939 or 2879
— to —
癸亥年 (Water Pig)
2940 or 2880
|Coptic calendar||−41 – −40|
|- Vikram Samvat||299–300|
|- Shaka Samvat||164–165|
|- Kali Yuga||3343–3344|
|Iranian calendar||379 BP – 378 BP|
|Islamic calendar||391 BH – 390 BH|
|Minguo calendar||1669 before ROC
|Seleucid era||554/555 AG|
|Thai solar calendar||785–786|
Year 243 (CCXLIII) 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 Arrianus and Papus (or, less frequently, year 996 Ab urbe condita). The denomination 243 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.
- Battle of Resaena: A Roman army under Timesitheus defeats the Persians at Resaena (Syria); King Shapur I is forced to flee to the Euphrates.
- Timesitheus becomes ill and dies under suspicious circumstances. Shapur I retreats to Persia, giving up all the territories he conquered.
- Emperor Gordian III appoints Philip the Arab as his new praetorian prefect and proceeds with his campaign in Mesopotamia.
- Cohors I Ubiorum, the garrison at castra Capidava in Scythia Minor, is replaced by Cohors I Germanorum civium romanorum until the end of the 3rd century AD.
- Gu Yong, minister of Wu (b. 168)
- Kan Ze, advisor of Wu
- Timesitheus, advisor and praetorian prefect (b. 190)
- Xue Zong, official of Wu