John Hay, 4th Marquess of Tweeddale,(1695 – 9 December 1762) was a Scottish nobleman.
Tweeddale had legal knowledge, and was appointed an Extraordinary Lord of Session in 1721, the last person to hold this office. He was one of the Scottish representative peers from 1722 to 1734 and from 1742 to 1762. On the downfall of Robert Walpole in February 1742, William Pulteney, 1st Earl of Bath had the office of Secretary of State for Scotland revived (it had been in abeyance since 1739), and the Marquess of Tweeddale appointed to it, also making Tweeddale Principal Keeper of the Signet and a Privy Counsellor.
English members of the Government rejected the idea that a Jacobite insurrection was at hand. Tweeddale, who was in London in 1745, was also sceptical, and even after he was aware that the Highlanders had left Perth in their march to the south, he wrote to the Lord Advocate, "I flatter myself they have been able to make no great progress", on the day when the Young Pretender entered the Palace of Holyroodhouse.
In February 1746, when the rebellion was still active, a ministerial crisis took place. When the King refused to admit Pitt to the Government, Henry Pelham, the Prime Minister resigned, along with the members of the administration who supported him. When Earl Granville and Tweeddale unsuccessfully attempted to form a Ministry, Pelham returned to office. Granville and Tweeddale were excluded from the reconstructed Government. The office of Secretary of State for Scotland was abolished a second time, and Tweeddale resigned his office of Keeper of the Signet.
He married Lady Elizabeth (or Frances) Carteret, daughter of John Carteret, 2nd Earl Granville in 1748, and they had four daughters and two sons. The eldest son died in infancy; the younger, George, became fifth Marquess, and died in 1770 at age 13. The title then devolved on his uncle, George Hay.
Hay was a Free Gardener. He was Initiated in the Dunfermline Lodge of Free Gardeners in 1721 and was immediately made Chancellor (Master) of the Lodge. His interest in the Lodge of Free Gardeners was an abiding one for he was again recorded as being Chancellor of the Lodge in 1742. There is no record of him becoming a Freemason.