|Millennium:||1st millennium BC|
|Centuries:||6th century BC – 5th century BC – 4th century BC|
|Decades:||500s BC 490s BC 480s BC – 470s BC – 460s BC 450s BC 440s BC|
|Years:||481 BC 480 BC 479 BC – 478 BC – 477 BC 476 BC 475 BC|
|478 BC by topic|
|Gregorian calendar||478 BC|
|Ab urbe condita||276|
|Ancient Egypt era||XXVII dynasty, 48|
|- Pharaoh||Xerxes I of Persia, 8|
|Ancient Greek era||75th Olympiad, year 3|
|Chinese calendar||壬戌年 (Water Dog)
2219 or 2159
— to —
癸亥年 (Water Pig)
2220 or 2160
|Coptic calendar||−761 – −760|
|Ethiopian calendar||−485 – −484|
|- Vikram Samvat||−421 – −420|
|- Shaka Samvat||N/A|
|- Kali Yuga||2624–2625|
|Iranian calendar||1099 BP – 1098 BP|
|Islamic calendar||1133 BH – 1132 BH|
|Minguo calendar||2389 before ROC
|Thai solar calendar||65–66|
|Wikimedia Commons has media related to 478 BC.|
Year 478 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Mamercus and Structus (or, less frequently, year 276 Ab urbe condita). The denomination 478 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.
- Despite Spartan opposition, Athens is refortified as well as rebuilt after the Persian destruction of the city.
- With the help of the Athenian statesman and general, Cimon, Aristides commands an Athenian fleet of 30 ships that the Spartan commander Pausanias leads to free the Greek cities on Cyprus and capture Byzantium from the Persians and their Phoenician allies.
- While Pausanias is occupying Byzantium, his arrogance and his adoption of Persian clothing and manners offends the allies and raises suspicions of disloyalty. Pausanias is recalled to Sparta, where he is tried and acquitted of the charge of treason, but he is not restored to his command.