Alexander Comyn, 2nd Earl of Buchan (died 1289) was a Scoto-Norman magnate who was one of the most important figures in the 13th century Kingdom of Scotland.

He was the chief counsellor of Alexander III, King of Alba (Scotland) for the entire period of the king's majority and as Scotland's leading magnate, played a key role in safeguarding the independence of the Scottish monarchy.

During his long career, Alexander Comyn was Justiciar of Scotia (1258–1289), Constable of Scotland (1275–1289),[1] Sheriff of Wigtown (1263–1266), Sheriff of Dingwall (1264–1266), Baillie of Inverie (in Knoydart) and finally, Guardian of Scotland (1286–1289) during the first interregnum following the death of Alexander III.

In 1284 he joined with other Scottish noblemen who acknowledged Margaret of Norway as the heiress to King Alexander.

Alexander had at least nine children with his wife, Elizabeth (or Isabel or Isabella), daughter of Roger de Quincy, 2nd Earl of Winchester, and Helen of Galloway: This Scottish biographical article is a stub.