William de Haya, who flourished about 1170, is said to have been the father of two sons, of whom the younger, Robert, was ancestor of the Marquises of Tweeddale. From the elder son, William, came the house of Erroll, and his descendant, Sir William Hay, was created Earl of Erroll in 1453.
The Hays of Erroll hold the office of Hereditary Constable of Scotland, this title having been conferred in 1314 by King Robert Bruce on the grandfather of the 1st Earl.
The 4th Earl fell at Flodden in 1513, and the 13th Earl, dying unmarried in 1717, was succeeded by his sister as Countess of Erroll. But on her death in 1758, without issue, the title went to James Boyd, son and heir of the 4th (and attainted) Earl of Kilmarnock, by his wife, Ann Livingstone, who was the daughter and heiress of the Earl of Linlithgow and Callander, and his wife, Margaret Hay, sister of the above-mentioned Countess of Erroll.
On succeeding to the title James Boyd changed his name to Hay, in accordance with clan law; and his descendants succeeding to the Earldom have been continual Chiefs of the Clan Hay.

Chief: Countess of Erroll.
Patronymic: MacGaradh Mor.
Clan Seats: Mote of Erroll, Perthshire; Old Slains Castle, Aberdeenshire.
Slogan: A Hay ! A Hay ! A Hay !
Plant: Mistletoe.
Memorials: Inchaffray Abbey.