St Mary's Church is the parish church in the town of Amersham in Buckinghamshire, England. It is located in Old Amersham.
The church dates from the 13th century with additions in the 14th century. It was also restored in 1890, and the external appearance dates from this time. There are many monuments in the church.
The bells are still rung in the church tower.
The body of the murderer Ruth Ellis was reburied in the churchyard extension of St Mary's Church. The headstone in the churchyard was inscribed "Ruth Hornby 1926–1955". Her son, Andy, destroyed the headstone shortly before he committed suicide in 1982.