William Hay, 4th Earl of Erroll

William Hay, 4th Earl of Erroll (1470 –  9 September 1513), styled as Lord Hay until 1507, was a Scottish peer and soldier. He was killed at the Battle of Flodden.

Biography
William Hay was the son of William Hay, 3rd Earl of Erroll. He had double royal lineage: his grandfather, William Hay, 1st Earl of Erroll was a great-great grandson of King Robert II of Scotland; and his maternal grandfather was James I of Scotland.

He served as the Lord High Constable of Scotland, a hereditary title that was, after the king, the supreme officer of the Scottish army. He was killed on 9 September 1513 in the Battle of Flodden, near Branxton, Northumberland. He died alongside his younger brother Thomas, King James IV of Scotland and more than a dozen dukes and earls in a decisive English victory.

Marriage and issue
He married Christian Lyon, daughter of John Lyon, 3rd Lord Glamis, and had two children:
 * 1) William Hay, 5th Earl of Erroll (c. 1495, Errol, Perthshire, Scotland – 28 July 1522 in Edinburgh)
 * 2) Lady Isabel Hay

He married secondly Margaret Kinloch of Cruvie, widow of Sir James Sandilands, 5th feudal baron of Calder.