The honorific title meaning “the Great” used for Caesar’s rival Pompey was Magnus.
Pompey’s full Roman name was Gnaeus Pompeius Magnus. Magnus was his cognomen, the part of a Roman name that could identify a family branch or commemorate a notable quality. The title is usually translated as “the Great,” producing the familiar English name Pompey the Great.
According to the traditional account, Pompey’s patron Sulla awarded him the name after his early military successes during the civil wars of the 80s BC. It may also have echoed Pompey’s admiration for Alexander the Great. Pompey later became one of the Republic’s most powerful commanders, winning victories in Spain, against Mediterranean pirates, and in the East.
Magnus should not be confused with Pompey’s political faction, the Optimates, or with later Roman titles such as Pius and Felix. Those were separate epithets or political labels, whereas Magnus was part of Pompey’s name and public identity. His rivalry with Julius Caesar eventually led to civil war and Pompey’s defeat at Pharsalus in 48 BC.