A diocese is a group of churches led by a bishop. Within the ACNA, there are about 30 dioceses. Most dioceses are geographically organized. Several others are non-geographic; their relationships are based on common affinities, common histories, or missional emphases.
A diocese sometimes contains deaneries (ie. regions), which are led by a dean.
The purpose of a diocese is to equip local congregations for the mission of the Church. This is done by maintaining doctrinal fidelity, vetting and ordaining new clergy, supporting existing clergy with pastoral care and discipline, confirming the faith of youth and adults, and providing congregations with ministry resources (policies, guidelines, and best practices).
