St. Mary's Church is a Grade I listed Anglican church in Chesham, Buckinghamshire, and is part of the Diocese of Oxford. Built on the site of a Bronze Age stone circle of puddingstones, parts of the church building date to the 12th century. Remodelled in the 15th and 17th centuries, the church is architecturally a mixture of English Gothic styles. Weakened by additions to the church tower and undermined by burials in and around the church, by the 19th century the building was structurally unsound. The church was remodelled and strengthened in the 1860s by George Gilbert Scott and again in the 20th century by Robert Potter.
Formerly part of the Diocese of Lincoln, it served what was historically the largest parish in Buckinghamshire, and the church traditionally had two vicars. Initially the advowson was held jointly by a pair of prominent local families, but in the wake of the 12th century civil wars of the reign of King Stephen (1135–1154), the advowsons were granted to the monks of Woburn Abbey and to the Abbey of Saint Mary de Pratis in Leicester, each of whom appointed their own vicars to the parish. After the Dissolution of the Monasteries Woburn Abbey, together with its half of the advowson, was granted to the Earls of Bedford, while the half that had belonged to Leicester Abbey passed through a succession of private owners. In 1769 the Duke of Bedford acquired the Leicester half of the advowson and unified the parish, and from then on the parish was served by a single vicar.
The town of Chesham grew rapidly in the 19th century. After the parish was transferred to the Diocese of Oxford, reforms introduced by the Bishop of Oxford, Samuel Wilberforce, led to the parish being partitioned, eventually becoming four independent parishes (Chesham, Latimer, Waterside and Ashley Green). In 1980 it was decided to reverse this decision, and over the 1980s and 1990s three of these parishes (Chesham, Waterside and Ashley Green) were reunited under St. Mary's Church.