|Millennium:||1st millennium BC|
|Centuries:||4th century BC – 3rd century BC – 2nd century BC|
|Decades:||310s BC 300s BC 290s BC – 280s BC – 270s BC 260s BC 250s BC|
|Years:||287 BC 286 BC 285 BC – 284 BC – 283 BC 282 BC 281 BC|
|284 BC by topic|
|Gregorian calendar||284 BC|
|Ab urbe condita||470|
|Ancient Egypt era||XXXIII dynasty, 40|
|- Pharaoh||Ptolemy I Soter, 40|
|Ancient Greek era||124th Olympiad (victor)¹|
|Chinese calendar||丙子年 (Fire Rat)
2413 or 2353
— to —
丁丑年 (Fire Ox)
2414 or 2354
|Coptic calendar||−567 – −566|
|Ethiopian calendar||−291 – −290|
|- Vikram Samvat||−227 – −226|
|- Shaka Samvat||N/A|
|- Kali Yuga||2818–2819|
|Iranian calendar||905 BP – 904 BP|
|Islamic calendar||933 BH – 932 BH|
|Minguo calendar||2195 before ROC
|Seleucid era||28/29 AG|
|Thai solar calendar||259–260|
|Wikimedia Commons has media related to 284 BC.|
Year 284 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Tucca and Denter/Dentatus (or, less frequently, year 470 Ab urbe condita). The denomination 284 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 Gallic tribe called the Senones, who has settled on the Adriatic coast north of Picenum, attacks Arretium in Etruria. While attempting to relieve this allied city, the Romans under the command of Lucius Caecilius Metellus Denter suffer a costly defeat in the Battle of Arretium. Aroused by this disaster, a Roman army under Manius Curius Dentatus invades the Senones' territory, defeating them and driving them out of the Italian peninsula.
- Ptolemy I's eldest (legitimate) son, Ptolemy Keraunos, whose mother, Eurydice, the daughter of Antipater, had been repudiated by the new King Ptolemy II, flees Egypt to the court of Lysimachus, the king of Thrace, Macedon and Asia Minor.
- Lysimachus' wife, Arsinoe, being keen to gain the succession to the kingdom of Thrace for her sons in preference to Agathocles (the eldest son of Lysimachus), intrigues against him with the help of her brother Ptolemy Keraunos. They accuse him of conspiring with Seleucus to seize the throne, and Agathocles is put to death. This atrocious deed by Lysimachus and his family arouses great indignation. Many of the cities in Asia Minor revolt and some of his most trusted friends desert him.
- Agathocles' widow Lysandra flees with their children and with Alexander, Agathocles' brother, to the court of Seleucus, who at once invades Lysimachus' territory in Asia Minor.
- Lucius Caecilius Metellus Denter, Roman consul and general (killed in the Battle of Arretium) (b. c. 320 BC)
- Ardvates, governor and later ruler of Armenia who founds a dynasty that will rule until 211 BC
- Agathocles, son of King Lysimachus of Thrace