On September 4, A.D. 476, child emperor Romulus Augustulus (Dominus Noster Romulus Augustus Pius Felix Augustus) was deposed by barbarian soldier (and Arian Christian) Odoacer, who proclaimed himself “King of Italy,” yet represented himself as the client of Zeno, the Eastern Roman Emperor in Constantinople.
September 4, 476, is the traditional end date for the Western Roman Empire.