Ely Cathedral, formally the Cathedral Church of the Holy and Undivided Trinity, is an Anglican cathedral in the city of Ely, Cambridgeshire, England.

The cathedral has its origins in AD 672 when St Etheldreda built an abbey church. The present building dates back to 1083, and it was granted cathedral status in 1109. Until the Reformation it was the Church of St Etheldreda and St Peter, at which point it was refounded as the Cathedral Church of the Holy and Undivided Trinity of Ely, continuing as the principal church of the Diocese of Ely, in Cambridgeshire. It is the seat of the Bishop of Ely and a suffragan bishop, the Bishop of Huntingdon. Architecturally, it is outstanding both for its scale and stylistic details. Having been built in a monumental Romanesque style, the galilee porch, lady chapel and choir were rebuilt in an exuberant Decorated Gothic. Its most notable feature is the central octagonal tower, with lantern above, which provides a unique internal space and, along with the West Tower, dominates the surrounding landscape. Ely Cathedral is a major tourist destination, receiving around 250,000 visitors per year, and sustains a daily pattern of morning and evening services.