Year 203 BC was a year of the pre-Julian Roman calendar.
|Millennium:||1st millennium BC|
|Centuries:||4th century BC – 3rd century BC – 2nd century BC|
|Decades:||230s BC 220s BC 210s BC – 200s BC – 190s BC 180s BC 170s BC|
|Years:||206 BC 205 BC 204 BC – 203 BC – 202 BC 201 BC 200 BC|
|203 BC by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishments and disestablishments categories|
|Establishments – Disestablishments|
|Gregorian calendar||203 BC|
|Ab urbe condita||551|
|Ancient Egypt era||XXXIII dynasty, 121|
|- Pharaoh||Ptolemy V Epiphanes, 1|
|Ancient Greek era||144th Olympiad, year 2|
|Balinese saka calendar||N/A|
|Chinese calendar||丁酉年 (Fire Rooster)|
2494 or 2434
— to —
戊戌年 (Earth Dog)
2495 or 2435
|Coptic calendar||−486 – −485|
|Ethiopian calendar||−210 – −209|
|- Vikram Samvat||−146 – −145|
|- Shaka Samvat||N/A|
|- Kali Yuga||2898–2899|
|Iranian calendar||824 BP – 823 BP|
|Islamic calendar||849 BH – 848 BH|
|Minguo calendar||2114 before ROC|
|Seleucid era||109/110 AG|
|Thai solar calendar||340–341|
−76 or −457 or −1229
— to —
−75 or −456 or −1228
By place change
- The Roman general, Publius Cornelius Scipio makes a surprise attack on the Carthaginians camp and destroys it. He defeats the army in the Battle of the Great Plains. The Numidian king, Syphax, and the Carthaginian leader, Hasdrubal Gisco, both escape.
- The Roman general, Gaius Laelius, and Rome's Numidian ally, Masinissa, follow Syphax towards Cirta, the Numidian capital. Syphax is captured and later dies in the Italian town of Alba Fucens.
- Masinissa becomes king of both the Massyli and the Massaesyli tribes in Numidia. He remains a loyal ally to the Romans.
- Hasdrubal Gisco gets the Carthaginians to form a new army and to send for Hannibal to return home from Italy. Hannibal finally leaves Italy and returns to Carthage.
- The Carthaginian general, Mago Barca, is defeated and wounded by the Romans in a battle in Cisalpine Gaul. He dies of his wounds on the return voyage to Carthage.
- An agreement between Carthage and Rome is made. The Carthaginian armies accept Scipio's severe terms. But Hannibal gets the army ready for battle.
- Mago Barca, Carthaginian general during the Second Punic War against Rome who has accompanied his brother Hannibal on the invasion of Italy (b. 243 BC)
- Fabius Maximus Cunctator, Roman general and statesman (b. c. 275 BC)
- Syphax, Numidian king allied with the Carthaginians during the Second Punic War against Rome