Hyginus (Greek Hygeinos, 'healthy') was a Greek philosopher from Athens, per the Liber Pontificalis — the second of the four early popes of presumed Greek philosophical formation (with Telesphorus, Eleuterus, and the apologist-influenced Anicetus). He succeeded Telesphorus around AD 138 at the very start of the reign of Antoninus Pius.
The Liber Pontificalis attributes to him the formal institution of the clerical orders below the diaconate — the so-called 'minor orders' of acolyte, exorcist, lector, and porter — which became the foundational pattern of the Latin clerical hierarchy until the 1972 Vatican II reform replaced the medieval minor orders with the ministries of lector and acolyte. He also confronted the early gnostic teachers Valentinus and Cerdo, who arrived at Rome during his reign and began to teach there.
His four-year pontificate was brief and is sparsely documented; the Liber Pontificalis records his martyrdom but no specific circumstances are known. He is buried at the Vatican near the tomb of Peter.