Marquess of Downshire is a title in the Peerage of Ireland. It was created in 1789 for Wills Hill, 1st Earl of Hillsborough, a former Secretary of State.

Trevor Hill, 1st Viscount Hillsborough was an Anglo-Irish landowner and politician who sat in the Irish House of Commons from 1713 to 1715 and in the British House of Commons from 1715 to 1722.