Constantine III was a Roman Emperor who ruled briefly in 407 AD. He was proclaimed emperor by his troops in Britain and is often considered a usurper. His reign was marked by attempts to assert control over the western provinces of the Roman Empire, which were facing increasing threats from various barbarian groups. His rule was short-lived, lasting only about a year before he was defeated by the forces of Honorius, the legitimate emperor of the Western Roman Empire. After his defeat, Constantine III was captured and executed, marking the end of his claim to the imperial throne.