Pachomius, who died around AD 345 in Tabennisi, Egypt, was one of the founders of Christian monasticism.

Pachomius was a young Egyptian who according to tradition was raised a pagan and became a Christian after service in the Roman army.

Pachomius set out to lead the life of a hermit near St. Anthony of Egypt, whose practices he imitated. Like many later monastic founders, he was quickly swamped with young men seeking his guidance in imitating his life, and became the founder of a monastery by default.

Earlier monasticism had been solitary or eremitic. Male or female monastics lived in individual huts or caves and met only for occasional worship services. Pachomius seems to have invented the community or cenobitic organization, in which male or female monastics lived together and had their possessions in common under the leadership of an abbot or abbess. This first cenobitic monastery was in Tabennisi, Egypt. He is also credited with being the first Christian to use and recommend use of a prayer rope. He was visited once by Basil of Caesarea, who took many of his ideas and implemented them in Caesarea, where Basil also made some adaptations of his own.

There were several written documents available in the 5th Century that purported to be monastic rules or organizational regulations written by Pachomius. These were translated into Latin by Jerome.

See St. Benedict and Desert Fathers.