theologian-priest whose work De viris illustribus (“On Famous Men”) constitutes the sole source for biographical and bibliographical information on numerous early Eastern and Western Christian authors.

Having read widely in Greek and Latin, Gennadius, between 467 and 480, drew up his continuation of the chronicle De viris illustribus, which had been initiated by St. Jerome after the identically titled classic model of the 2nd-century Latin historian Suetonius. Gennadius' version comprised 91 biographies of late 4th- and 5th-century Greek and Latin theological writers; the work was augmented to 100 biographies by later editors.

Gennadius appears to have supported the position of the Semi-Pelagian authors. He took a theological middle ground between the heretical stance of the 5th-century Irish monk Pelagius, who formulated a doctrine that man's basic capacity and responsibility enable him to choose a moral life without supernatural aid, and the strict anti-Pelagians, notably St. Augustine of Hippo (354–430), who attributed man's entire ability for moral action to God's inspiration.