the oldest surviving Christian church order, probably written in Egypt or Syria in the 2nd century. In 16 short chapters it deals with morals and ethics, church practice, and the eschatological hope (of the Second Coming of Christ at the end of time) and presents a general program for instruction and initiation into the primitive church.

Some early Christian writers considered the Didachē canonical, and Egyptian authors and compilers quoted it extensively in the 4th and 5th centuries. Eusebius of Caesarea quoted it in his Ecclesiastical History (early 4th century), and it formed the basis of chapter 7 of the 4th-century Apostolic Constitutions, a collection of early Christian ecclesiastical law. It was known only through such references in early Christian works until a Greek manuscript of it, written in 1056, was discovered in Istanbul in 1873 by the metropolitan Philotheos Bryennios (Bryennios, Philotheos). He published it in 1883. Two fragments of the work were later discovered, a 4th-century Greek papyrus in Oxyrhynchus, Egypt, and a 5th-century Coptic papyrus in the British Museum.

The Didachē is not a unified and coherent work but a compilation of regulations that had acquired the force of law by usage in scattered Christian communities. Evidently several pre-existing written sources were used and were compiled by an unknown editor.

Chapters 1–6 give ethical instruction concerning the two ways, of life and of death, and reflect an early Christian adaptation of a Jewish pattern of teaching in order to prepare catechumens (candidates for Christian baptism). Chapters 7–15 discuss baptism, fasting, prayer, the Eucharist, how to receive and test traveling apostles and prophets, and the appointment of bishops and deacons. Chapter 16 considers the signs of the Second Coming of the Lord.