Historical Events in 421 AD Feb 8 Flavius Constantine becomes Co-Emperor as Emperor Constantius III of the Western Roman Empire with Honorius Mar 25 Friday at 12 PM - city of Venice founded Famous Weddings in 421 AD Jun 7 Eudocia A. Athenais marries Oostromeins emperor Theodosius II Famous People Who Died in 421 AD Sep 2 Flavius Constantine III, Emperor of Western Roman Empire, dies at about 51 420 AD History by Year 422 AD