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.