Eusebius of Caesarea (s/; Greek: Εὐσέβιος τῆς Καισαρείας, Eusébios tés Kaisareías; AD 260/265 – 339/340), also known as Eusebius Pamphili (from the Greek: Εὐσέβιος τοῦ Παμϕίλου), was a historian of Christianity, exegete, and Christianpolemicist. He became the bishop of Caesarea Maritima about 314 AD. Together with Pamphilus, he was a scholar of the Biblical canon and is regarded as an extremely learned Christian of his time. He wrote Demonstrations of the Gospel, Preparations for the Gospel, and On Discrepancies between the Gospels, studies of the Biblical text. As "Father of Church History" (not to be confused with the title of Church Father), he produced the Ecclesiastical History, On the Life of Pamphilus, the Chronicle and On the Martyrs.
Little is known about the life of Eusebius. His successor at the See of Caesarea, Acacius, wrote a Life of Eusebius, a work that has since been lost. Eusebius' own surviving works probably only represent a small portion of his total output. Beyond notices in his extant writings, the major sources are the 5th-century ecclesiastical historians Socrates, Sozomen, and Theodoret, and the 4th-century Christian author Jerome. There are assorted notices of his activities in the writings of his contemporaries Athanasius, Arius, Eusebius of Nicomedia, and Alexander of Alexandria. Eusebius' pupil, Eusebius of Emesa, provides some incidental information.