Sir John Hay, 6th Baronet of Smithfield and Haystoun FRSE FSA (3 August 1788 – 1 November 1838) was a British baronet and politician. He sat as a Member of Parliament for Peeblesshire from 1831 to 1837. He was the son of Sir of Smithfield and Haystoun FRSE (1755-1830), banker and landowner, and Mary Elizabeth Forbes. His brother-in-law was the banker, George Forbes FRSE (1790-1857). He trained as an advocate and passed the Scottish bar in 1811. In 1820 he was elected a Fellow of the Royal Society of Edinburgh his proposer being George Forbes.