|Millennium:||1st millennium BC|
|Centuries:||6th century BC – 5th century BC – 4th century BC|
|Decades:||450s BC 440s BC 430s BC – 420s BC – 410s BC 400s BC 390s BC|
|Years:||431 BC 430 BC 429 BC – 428 BC – 427 BC 426 BC 425 BC|
|428 BC by topic|
|Gregorian calendar||428 BC|
|Ab urbe condita||326|
|Ancient Egypt era||XXVII dynasty, 98|
|- Pharaoh||Artaxerxes I of Persia, 38|
|Ancient Greek era||88th Olympiad (victor)¹|
|Chinese calendar||壬子年 (Water Rat)
2269 or 2209
— to —
癸丑年 (Water Ox)
2270 or 2210
|Coptic calendar||−711 – −710|
|Ethiopian calendar||−435 – −434|
|- Vikram Samvat||−371 – −370|
|- Shaka Samvat||N/A|
|- Kali Yuga||2674–2675|
|Iranian calendar||1049 BP – 1048 BP|
|Islamic calendar||1081 BH – 1080 BH|
|Minguo calendar||2339 before ROC
|Thai solar calendar||115–116|
|Wikimedia Commons has media related to 428 BC.|
Year 428 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Cossus and Cincinnatus or Cincinnatus and Atratinus (or, less frequently, year 326 Ab urbe condita). The denomination 428 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.
Hippolytus was first performed for City Dionysia and was written by Euripedes
- The chief city of Lesbos, Mytilene, revolts against Athenian rule. The Spartan admiral, Alcidas, leads 40 Peloponnesian alliance ships with the aim of assisting the inhabitants of Mytilene. However, the rebellion by Mytilene is crushed before his forces can arrive.
- Despite encouragement from the Ionian leaders to engage the Athenians, Alcidas declines. Rather, Alcidas leads his fleet to Cyllene where the Spartans resolve to strengthen the fleet and send it to Corcyra where a revolution has broken out. Spartan leaders, Brasidas and Alcidas, then defeat a fleet of Corcyran ships. However, they retire when word reaches them that 60 Athenian ships from Leucas under the command of Eurymedon have been dispatched to intercept them.
- The Greek colony of Cumae in Italy falls to the Samnites, who begin to take control of the Campanian plain.
- Euripides' play Hippolytus is performed in the Dionysia competition, the famous Athenian dramatic festival. The play is awarded first prize.
- Sophocles writes Oedipus the King.
- Anaxagoras, Greek philosopher (b. c. 500 BC)
- Lars Tolumnius, Etruscan King of Veii (killed in battle)