Serapion of Nitria or Serapion of Thmuis (Greek: Σεραπίων, romanized: Serapíon; Russian: Серапион) was an early Christian monk in Nitria, Lower Egypt, born in the third century AD. He was a companion of Anthony the Great, the abbot of the Monastery of Arsina in Nitria, and the bishop of Thmuis. His feast day in March 21 in the Orthodox Church.