Photios I of Constantinople
Theognostus (; c. 210 – c. 270) was a late 3rd century Alexandrian theologian. He is known from quotes by Athanasius and Photios I of Constantinople. Philip of Side says that he presided over the school of Alexandria after Pierius (AD 265). Although a disciple of Origen of Alexandria no reference of him can be found by Eusebius or Jerome. The main textual point of reference is derived from Athanasius.