The Church of St Martin, Cwmyoy, Monmouthshire, Wales, was begun in the 12th century, although most of the current structure dates from the 13th century. The church is most notable for its extreme tilt, the result of a landslide. This has led to many attempts to strengthen the church and prevent its collapse, through the use of massive tie beams and buttresses. The church is in the Gothic style, and has a chancel, nave, south porch, and western tower. A round-headed north window dates to the 12th century, and the nave roof has been dated to the late 13th or early 14th century. St Martin's is a Grade I listed building and an active parish church. It is dedicated to St Martin of Tours.