||Wikimedia Commons has media related to 203 BC.
Year 203 BC was a year of the pre-Julian Roman calendar.
- 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.
- Polybius, Greek historian, famous for his book called "The Histories" or "The Rise of the Roman Empire", covering in detail the period between 220 and 146 BC (d. 120 BC)