What happened
In AD 476 the Germanic commander Odoacer deposed Romulus Augustulus, the last western Roman emperor, the date conventionally taken as the end of the Western Empire.
Background
The West had long declined: division from the East (395), barbarian invasions and settlements, the sacks of Rome in 410 (Visigoths) and 455 (Vandals), shrinking revenue, and puppet emperors. Odoacer made himself king in Italy under nominal eastern authority.
Consequences
Roman political rule in the West ended, giving way to Germanic kingdoms, while the Eastern (Byzantine) Empire continued for another thousand years. Historians treat 476 as a symbolic marker rather than a sudden break, since Roman institutions and culture persisted.