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|Centuries:||2nd century – 3rd century – 4th century|
|Decades:||170s 180s 190s – 200s – 210s 220s 230s|
|Years:||200 201 202 – 203 – 204 205 206|
|203 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishment and disestablishment categories|
|Establishments – Disestablishments|
|Ab urbe condita||956|
|Chinese calendar||壬午年 (Water Horse)
2899 or 2839
— to —
癸未年 (Water Goat)
2900 or 2840
|Coptic calendar||−81 – −80|
|- Vikram Samvat||259–260|
|- Shaka Samvat||124–125|
|- Kali Yuga||3303–3304|
|Iranian calendar||419 BP – 418 BP|
|Islamic calendar||432 BH – 431 BH|
|Minguo calendar||1709 before ROC
|Seleucid era||514/515 AG|
|Thai solar calendar||745–746|
Year 203 (CCIII) 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 Plautianus and Geta (or, less frequently, year 956 Ab urbe condita). The denomination 203 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 Septimius Severus rebuilds Byzantium.
- Gaius Fulvius Plautianus and Publius Septimius Geta become Roman Consuls.
- An arch dedicated to Severus is erected near the Forum.
- The Portico of Octavia is reconstructed.
- Reign in India of Vijaya, Satavahana king of the Andhra.
- The Andhra empire is being broken apart into smaller and smaller independent principalities.
- Sun Quan battles Huang Zu at the Battle of Xiakou.
- Probable birth of Roman Emperor Marcus Aurelius Antoninus, better known as Elagabalus (d. 222)
- Zhuge Ke, son of Zhuge Jin, officer of the Wu Kingdom (d. 253)
- Perpetua, Christian saint (martyred)
- Felicitas, Christian saint (martyred)
- Ling Cao, general under Sun Ce and father of Ling Tong (killed by pirate Gan Ning)
- Sun Yi, younger brother of Sun Quan (b. 184)
- Wu Jing, general of the Han dynasty and brother-in-law of Sun Jian