The Church History (Latin: Historia Ecclesiastica or Historia Ecclesiae) of Eusebius of Caesarea was a 4th-century pioneer work giving a chronological account of the development of Early Christianity from the 1st century.
Eusebius made use of many ecclesiastical monuments and documents, acts of the martyrs, letters, extracts from earlier Christian writings, lists of bishops, and similar sources, often quoting the originals at great length so that his work contains materials not elsewhere preserved.