The Diocese of Chelmsford is a Church of England diocese, part of the Province of Canterbury. It was created on 23 January 1914 from part of the Diocese of St Albans. It covers Essex and part of East London. Since 1984 it is divided into three episcopal areas, each with its own area bishop. The diocese covers around 1,500 square miles (3,900 km2) with a population of more than 3 million. It has 463 parishes and 588 churches.

Chelmsford Cathedral in the city of Chelmsford, Essex, England, is dedicated to St Mary the Virgin, St Peter and St Cedd. It became a cathedral when the Anglican Diocese of Chelmsford was created in 1914 and is the seat of the Bishop of Chelmsford.