List of marquesses in the peerages of Britain and Ireland
This is a list of the 34 present and extant marquesses in the peerages of the Kingdom of England, Kingdom of Scotland, Kingdom of Great Britain, Kingdom of Ireland, and the United Kingdom of Great Britain and Ireland which became the United Kingdom of Great Britain and Northern Ireland in 1922. It does not mention any Marquessates held as a subsidiary title of a Duke.
Source: Wikipedia — List of marquesses in the peerages of Britain and Ireland (CC BY-SA 4.0)