William Hay, 17th Earl of Erroll (12 March 1772 – 26 January 1819), known as Lord Hay until 1778, was a Scottish peer.

Erroll was the son of James Hay, 15th Earl of Erroll and his second wife, Isabella Carr. He firstly married Jane Bell (d. 1793) in 1792, and they had one child together. Secondly, he married Alicia Eliot (d. 1812) in 1796, who was the sister-in-law of Sir Thomas Stapleton, 16th Baron Le Despencer; they had seven children together. Finally, Erroll married Harriet Somerville (d. 1864) in 1816.