A History of Christianity: The First Three Thousand Years is a 2009 book written by the English ecclesiastical historian Diarmaid MacCulloch, Professor of the History of the Church at the University of Oxford. It is a survey of the historical development of the Christian religion since its inception in the 1st century to the contemporary era. The first American edition was titled Christianity: The First Three Thousand Years, published in 2010 by Viking Press, imprint of Penguin Books.

Diarmaid Ninian John MacCulloch is an English academic and historian, specialising in ecclesiastical history and the history of Christianity. Since 1995, he has been a fellow of St Cross College, Oxford; he was formerly the senior tutor. Since 1997, he has been Professor of the History of the Church at the University of Oxford.