The 3rd century BC

975 sourced entries across 100 documented years, grouped into 10 decades. A century here runs 1900–1999 rather than 1901–2000, so its decades sit inside it exactly.

Decades

The 290s BC — 10 years, 57 entries
The 280s BC — 10 years, 79 entries
The 270s BC — 10 years, 78 entries
The 260s BC — 10 years, 80 entries
The 250s BC — 10 years, 76 entries
The 240s BC — 10 years, 96 entries
The 230s BC — 10 years, 90 entries
The 220s BC — 10 years, 125 entries
The 210s BC — 10 years, 129 entries
The 200s BC — 10 years, 165 entries

By subject

Conflict & Security in the 3rd century BC — 417 entries
Geopolitics & Diplomacy in the 3rd century BC — 83 entries
Religion & Belief in the 3rd century BC — 33 entries
Crime & Justice in the 3rd century BC — 33 entries
Exploration & Expansion in the 3rd century BC — 28 entries
Culture & Society in the 3rd century BC — 17 entries
Technology & Infrastructure in the 3rd century BC — 15 entries
Science & Discovery in the 3rd century BC — 8 entries

A few of the years

299 BCEThe consul Marcus Fulvius Paetinus sacks the Umbrian city of Nequinum, which Rome had been besieging since the previous year, and he possibly also fights with success against the Sabines.
287 BCEDemetrius besieges Athens without success. He leaves Antigonus in charge of the war in Greece, assembles all his ships and embarks with his troops to attack Caria and Lydia, provinces in Asia Minor controlled by Lysimachus.
275 BCEWhen Pyrrhus returns from Sicily, he finds himself vastly outnumbered by a superior Roman army under the command of consul Manius Curius Dentatus. After the inconclusive Battle of Beneventum, Roman commander and statesman, Gaius Fabricius Luscinus, negotiates a peace with Pyrrhus, after which Pyrrhus decides to end his campaign in Italy and return to Epirus, which results in the loss of all his Italian holdings.
263 BCEAlexander II of Epirus attacks and conquers the greater part of Macedonia. However, he is then driven out of both Macedonia and Epirus by Demetrius II, the son of King Antigonus II Gonatas of Macedonia.
251 BCEPaseas, the tyrant of the Greek city-state of Sicyon, is assassinated by Nicocles, with the acquiescence of the Macedonian king Antigonus II. Nicocles reigns as tyrant of Sicyon for only four months, during which period he drives into exile eighty of the city's citizens. Then the citadel of Sicyon is surprised in the night by a party of Sicyonian exiles, headed by a young nobleman, Aratus. The palace of the tyrant is set on fire, but Nicocles escapes from the city through a subterranean passage.
239 BCEQin Prime Minister Lü Buwei publishes the "Spring and Autumn Annals of Lü Buwei" (Lüshi Chunqiu).
227 BCESardinia and Corsica are made a combined province. Rome appoints, and in the future annually elects, two praetors (with autocratic consular powers) for this province and for Sicily.
215 BCEThe Roman law, Lex Oppia, is instituted by Gaius Oppius, a tribune of the plebs during the consulship of Quintus Fabius Maximus Verrucosus and Tiberius Sempronius Gracchus. The Lex Oppia is the first of a series of sumptuary laws introduced in Rome. It not only restricts women's wealth, but also their displaying it.