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

421 by topic
Leaders
Political entities State leaders Religious leaders
Categories
Deaths Establishments Disestablishments

421 in various calendars
Gregorian calendar	421 CDXXI
Ab urbe condita	1174
Assyrian calendar	5171
Balinese saka calendar	342–343
Bengali calendar	−172
Berber calendar	1371
Buddhist calendar	965
Burmese calendar	−217
Byzantine calendar	5929–5930
Chinese calendar	庚申年 (Metal Monkey) 3118 or 2911 — to — 辛酉年 (Metal Rooster) 3119 or 2912
Coptic calendar	137–138
Discordian calendar	1587
Ethiopian calendar	413–414
Hebrew calendar	4181–4182
Hindu calendars
- Vikram Samvat	477–478
- Shaka Samvat	342–343
- Kali Yuga	3521–3522
Holocene calendar	10421
Iranian calendar	201 BP – 200 BP
Islamic calendar	207 BH – 206 BH
Javanese calendar	305–306
Julian calendar	421 CDXXI
Korean calendar	2754
Minguo calendar	1491 before ROC 民前1491年
Nanakshahi calendar	−1047
Seleucid era	732/733 AG
Thai solar calendar	963–964
Tibetan calendar	阳金猴年 (male Iron-Monkey) 547 or 166 or −606 — to — 阴金鸡年 (female Iron-Rooster) 548 or 167 or −605

Year 421 (CDXXI) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Agricola and Eustathius (or, less frequently, year 1174 Ab urbe condita). The denomination 421 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

Roman Empire

February 8 – Constantius III is appointed co-emperor (Augustus) with his ineffectual brother-in-law, Honorius, and becomes the real ruler of the Western Roman Empire.
March 25 – Venice is founded at twelve o'clock noon (according to legend) with the dedication of the first church, San Giacomo, at the islet of Rialto (Italy).
June 7 – Emperor Theodosius II marries Aelia Eudocia, a woman of Greek origin. The wedding is celebrated at Constantinople with chariot racing in the Hippodrome.^[1]
September 2 – Constantius III dies suddenly of an illness; his wife Galla Placidia becomes, for the second time, a widow. She departs with her children Grata Honoria and Valentinian to the court of Constantinople.

Europe

Rugila, chieftain of the Huns, attacks the dioceses of Dacia and Thrace (Balkans). Theodosius II allows Pannonian Ostrogoths to settle in Thrace, to defend the Danube frontier.^{[citation needed]}
The Franks conquer new territories in their kingdom and sack the old Roman capital Augusta Treverorum (modern Trier).

Persia

Roman–Sassanid War: Theodosius II starts a war against the Sassanids, sending an expeditionary force under command of Ardaburius, and invades Mesopotamia.
Autumn – Ardaburius devastates Arzanene (Armenia) and forces the Persians to retreat to Nisibis (Syria). King Bahram V allies himself with the Lakhmid Arabs of Hirah.

Births

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Deaths

September 2 – Constantius III, emperor of the Western Roman Empire^[2]
Jin Gongdi, last emperor of the Jin Dynasty (b. 386)
Li Xun, ruler of the Chinese state Western Liang
Mary of Egypt, patron saint (approximate date)
Ravina I, rabbi (teacher) and Jewish Talmudist