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.

The diocese was created on 23 January 1914, as part of the provisions of the Bishoprics of Sheffield, Chelmsford and the County of Suffolk Act 1913. It covered the entire county of Essex and that part of Kent north of the River Thames (North Woolwich).^[5] The area had since 4 May 1877 been part of the Diocese of St Albans.^[6] Before 1 January 1846 the area was part of the Diocese of London and then the Diocese of Rochester.

The diocese covers a region of around 1,500 square miles (3,900 km²)^[3] and has a population of more than 3 million.^[2] It covers Essex and five East London boroughs of Barking and Dagenham, Havering, Newham, Redbridge, and Waltham Forest. The diocese has seen one of the strongest regenerations in Europe, which continues. The Thames Gateway, the M11 corridor, Stansted and Southend airports, Harwich, Tilbury, London Gateway, Purfleet ports and most of the housing built in connection with the London 2012 Olympics are in the diocese. It is co-terminous with the boundaries of the Catholic Diocese of Brentwood.

The diocese of Chelmsford is overseen by the Bishop of Chelmsford. Since the area scheme was created in 1983^[7] and inaugurated in January 1984,^[8] the diocese has been divided into three episcopal areas which are overseen by an area bishop. The diocese is divided further into archdeaconries, each divided into a number of deaneries.^[9]

The suffragan See of Colchester was created in 1882, for the Diocese of St Albans until 1914. Barking in 1901 also for St Albans, and Bradwell in 1968.

The diocese has 463 parishes^[1] and a total of 588 churches.^[2]