St. Eusebius of Caesarea was a Christian historian and bishop who lived during the early 4th century. He is best known for his work, "Ecclesiastical History," which chronicles the development of the Christian Church from the time of Christ to his own era. Eusebius is often referred to as the "Father of Church History" for his detailed accounts and insights into early Christianity. Born around 260 AD in Palestine, Eusebius became the bishop of Caesarea Maritima. He played a significant role in the early Church, particularly during the reign of Emperor Constantine, who legalized Christianity. Eusebius's writings also include biblical texts and apologetic works, contributing to the understanding of early Christian theology and the historical context of the Church.