William Hay, 10th Earl of Erroll PC (before 1597 – 7 December 1636) was a Scottish nobleman.

He was the eldest son of Francis Hay, 9th Earl of Erroll by his third wife, Lady Elizabeth, daughter of William Douglas, 6th Earl of Morton.

In January 1611, with the Earl of Pembroke and Lord Windsor, he escorted a French diplomat, the Marshal de Laverdin, from Croydon to Lambeth.

He also succeeded to the title of Lord High Constable of Scotland, and took part in the Scottish coronation of King Charles I of Holyrood Abbey on 18 June 1633.

The earl lived such an extravagant lifestyle that he was forced to sell off the family's namesake lands in Errol, which had been granted to his forebears by King William the Lion in the 12th century.