421 BC

Millennium:	1st millennium BC
Centuries:	6th century BC 5th century BC 4th century BC
Decades:	440s BC 430s BC 420s BC 410s BC 400s BC
Years:	424 BC 423 BC 422 BC 421 BC 420 BC 419 BC 418 BC

421 BC in various calendars

Gregorian calendar	421 BC CDXXI BC
Ab urbe condita	333
Ancient Egypt era	XXVII dynasty, 105
- Pharaoh	Darius II of Persia, 3
Ancient Greek era	89th Olympiad, year 4
Assyrian calendar	4330
Balinese saka calendar	N/A
Bengali calendar	−1013
Berber calendar	530
Buddhist calendar	124
Burmese calendar	−1058
Byzantine calendar	5088–5089
Chinese calendar	己未年 (Earth Goat) 2277 or 2070     — to — 庚申年 (Metal Monkey) 2278 or 2071
Coptic calendar	−704 – −703
Discordian calendar	746
Ethiopian calendar	−428 – −427
Hebrew calendar	3340–3341
Hindu calendars
- Vikram Samvat	−364 – −363
- Shaka Samvat	N/A
- Kali Yuga	2680–2681
Holocene calendar	9580
Iranian calendar	1042 BP – 1041 BP
Islamic calendar	1074 BH – 1073 BH
Javanese calendar	N/A
Julian calendar	N/A
Korean calendar	1913
Minguo calendar	2332 before ROC 民前2332年
Nanakshahi calendar	−1888
Thai solar calendar	122–123
Tibetan calendar	阴土羊年 (female Earth-Goat) −294 or −675 or −1447     — to — 阳金猴年 (male Iron-Monkey) −293 or −674 or −1446

Year 421 BC was a year of the pre-Julian Roman calendar. At the time, it was known in Rome as the Year of the Consulship of Vibulanus and Barbatus (or, less frequently, year 333 Ab urbe condita). The denomination 421 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.

Events

By place

Greece

• Nicias, the leader of the aristocratic and peace party in Athens and Pleistoanax, King of Sparta, negotiate the Peace of Nicias between Athens and Sparta, which brings a temporary end to the Peloponnesian War. The essence of the Peace of Nicias is a return to the antebellum period with most wartime gains being returned. Seventeen representatives from each side swear an oath to uphold the treaty, which is meant to last for one generation (30 years: meaning they are not responsible for the next generation's decision). All of Sparta's allies agree to sign the peace except for the Boeotians, Corinth, Elis, and Megara.
• Alcibiades engineers an anti-Spartan alliance between Athens and the democracies of Argos, Mantinea and Elis.

Italy

• The city of Cumae, the most northerly of the Greek colonies in Italy, falls to the Samnites.

By topic

Art

• The construction of the Porch of the Maidens (the Caryatid Porch) commences at the Erechtheion which is part of the Acropolis in Athens.

Drama

• Aristophanes' play Peace is performed.

Deaths

• Cratinus, Greek comedy author (approximate date) (b. 520 BC)