The Cathedral of St Andrew is a ruined Roman Catholic cathedral in St Andrews, Fife, Scotland. 

It was built in 1158 and became the centre of the Medieval Catholic Church in Scotland. It fell into disuse and ruin after Catholic mass was outlawed during the 16th-century Scottish Reformation. The ruins indicate that the building was approximately 119m (391 feet) long, and is the largest church to have been built in Scotland.