3rd century BC

Centuries:	4th century BC - 3rd century BC - 2nd century BC
Decades:	00s 10s 20s 30s 40s 50s 60s 70s 80s 90s

Events

The first two Punic Wars between Carthage and Rome over dominance in western Mediterranean
Rome conquers Spain
Gaulish migration to Macedonia, Thrace and Galatia
281 BCE Antiochus I Soter, on the assassination of his father Seleucus becomes emperor of the Seleucid empire.
273 BCE to 252 BCE Ashoka the Great ruled the Mauryan Empire
261 BCE Antiochus II Theos, 2nd son, at the death of his father becomes emperor of the Seleucid empire.
214 BCE Qin Shi Huang Qin Dynasty ordered contruction of the Great Wall of China.
Indian traders regularly visited Arabia
Scythians occupy Sogdiana, in modern-day Uzbekistan.
Han dynasty was founded (202 BC - 8 AD).

Mencius, Chinese philosopher and sage (371 - 289 BC).
Euclid, geometer (c. 365 - 275 BC).
Ashoka, Mauryan ruler of India 273 BC - 232 BC.
Archimedes of Syracuse, mathematician, physicist, and engineer (c. 287 - 212 BC).
The Ptolemaic dynasty rules Egypt
- Ptolemy I Soter (305 BC-282 BC) and his wives Eurydice and
- Ptolemy II Philadelphos (284 BC-246 BC) and his wives Arsinoe I and Arsinoe II Philadelphos.
- Ptolemy III Euergetes I (246 BC-222 BC) and his wife Berenice II.
- Ptolemy IV Philopater (222 BC-204 BC) and his wife Arsinoe III.
- Ptolemy V Epiphanes (204 BC-180 BC) and his wife Cleopatra I.
Eratosthenes (c. 276 - 194 BC), Greek mathematician, geographer and astronomer.
Apollonius of Perga, mathematician (c. 262 - 190 BC).
Qin Shi Huang, Chinese Emperor (259 - 210 BC, reigned 246 - 210 BC).
Hannibal, military leader of Carthage (247 - 182 BC).
the "second" Brennus, Gaulish chieftain, invades Macedonia in 279 BC

Eratosthenes accurately calculates diameter of the Earth
Weiqi well-established in China, and may date back to the 2nd millennium BC
Stone of Canopus (for Ptolemy III), No. 1, in Rosetta Stone Series of 3 stones. Implements Leap year in Egypt. Leap year not formally recognized until Caesar in 55 B.C.