Lucius Aelius Seianus (20 BC – October 18, AD 31), commonly known as Sejanus (English pronunciation: ), was an ambitious soldier, friend and confidant of the Roman Emperor Tiberius. An equestrian by birth, Sejanus rose to power as prefect of the Roman imperial bodyguard, known as the Praetorian Guard, of which he was commander from AD 14 until his death in AD 31.