Saint Serapion (also Sarapion) was a fourth-century bishop of Thmuis in the Nile Delta. He was a prominent supporter of Athanasius in the struggle against Arianism and a close friend of St Anthony the Great. To distinguish him from the many others who shared the same name, he is sometimes referred to with the title "Scholasticus" for his learning. He is remembered in the Church as the author of the Euchologion of Serapion of Thmuis. He is commemorated on March 21.
Source: Wikipedia: Serapion of Thmuis