The Early Church Fathers are the early and influential theologians and writers in the Christian Church, particularly those of the first five centuries of Christian history. The term is used of writers and teachers of the Church, not necessarily saints. It is generally not meant to include the New Testament authors, though in the early Church some writing of Church Fathers were considered canonical.
Writings of Clement (of Rome), Mathetes, Polycarp, Ignatius, Barnabas, Papias, Justin Martyr, Irenaeus.
The Didache, or The Teaching of the Twelve Apostles, is a brief early Christian treatise, dated by most scholars to the late first or early 2nd century.