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Year 223 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Flaminius and Philus (or, less frequently, year 531 Ab urbe condita). The denomination 223 BC 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 Seleucid king Seleucus III is assassinated by members of his army while on campaign against Attalus of Pergamon in Phrygia.
• Seleucus III is succeeded by his younger brother, Antiochus III.^[1]

• Gaius Flaminius is elected consul for the first time and, with his co-consul Publius Furius Philus, he forces the Gauls south of the Alps to submit to Rome, creating the province of Cisalpine Gaul.

• The Spartan king Cleomenes III destroys and burns the city of Megalopolis but the inhabitants are saved by Philopoemen who leads the defence of the city until the inhabitants can escape.
• The king of Macedonia, Antigonus III Doson, restores Macedonian influence in the Peloponnese for the first time in almost two decades. After signing alliances with the Achaeans, Boeotians, Thessalians and the Acarnanians, Antigonus invades the Peloponnese and drives the Spartans out of Argos, taking Orchomenus and Mantineia in the process.

• King Diodotus II of Bactria is killed by a usurper, Euthydemus I, founder of the Greco-Bactrian Euthydemid dynasty.

• The Qin generals Wang Jian and Meng Wu defeat the Chu general Xiang Yan and the king of Chu, Lord Changping. Lord Changping is killed, and Xiang Yan commits suicide soon afterwards.^[2]

• Lord Changping, the last king of Chu, one of the Seven Warring States in ancient China.
• Diodotus II, King of Bactria, the son and successor of Diodotus I (approximate date) (b. c. 252 BC)
• Seleucus III, king of the Seleucid dynasty from 226 BC (assassinated) (b. c. 243 BC)