Marquess of Winchester is a title in the Peerage of England that was created in 1551 for the prominent statesman William Paulet, 1st Earl of Wiltshire. It is the oldest of six surviving English marquessates; therefore its holder is considered the premier marquess of England. It is also now the only marquessate in the Peerage of England not being subsidiary to a higher title. The current holder is Christopher Paulet, 19th Marquess of Winchester, whose son uses the courtesy title Earl of Wiltshire.

William Paulet, 1st Marquess of Winchester, styled Lord St John between 1539 and 1550 and Earl of Wiltshire between 1550 and 1551, was an English Lord High Treasurer, Lord Keeper of the Great Seal, and statesman.