The Cathedral of St Andrew is a ruined cathedral in St Andrews, Fife, Scotland. It was built in 1158 and became the centre of the Medieval Catholic Church in Scotland as the seat of the Archdiocese of St Andrews and the Bishops and Archbishops of St Andrews. It fell into disuse and ruin after Catholic mass was outlawed during the 16th-century Scottish Reformation. It is currently a monument in the custody of Historic Environment Scotland. The ruins indicate that the building was approximately 119 m (390 ft) long, and is the largest church to have been built in Scotland.

St Andrews is a town on the east coast of Fife in Scotland, 10 miles southeast of Dundee and 30 miles northeast of Edinburgh. St Andrews had a recorded population of 16,800 as of 2011, making it Fife's fourth-largest settlement and 45th most populous settlement in Scotland.