The Marquess of Trelissick (also called Marquis of Trelessick) is a title in the Jacobite Peerage of England.

It was the only non-subsidiary title at the rank of Marquess in the English Jacobite Peerage, before becoming a subsidiary of the Duke of Tyrconnell.

In 1715 he was active in proclaiming James Francis Edward Stuart (the Old Pretender) on the death of Queen Anne.

[3][4] For his commitment, he was created Marquess of Trelissick in the Jacobite Peerage of England, on 20 June 1715.

He also holds the Jacobite Peerage of Baron Bourke, as heir-male, and Duke of Tyrconnell, as direct heir-general.