A courtesy title is a form of address in systems of nobility used for children, former wives and other close relatives of a peer, as well as certain officials such as some judges and members of the Scottish gentry. These styles are used "by courtesy" in the sense that persons referred to by these titles do not in law hold the substantive title. There are several different kinds of courtesy titles in the British peerage system.

Peerages in the United Kingdom form a legal system comprising both hereditary and lifetime titles, composed of various ranks, and within the framework of the Constitution of the United Kingdom form a constituent part of the legislative process and the British honours system. The British monarch is considered the fount of honour and is notionally the only person who can grant peerages, though there are many conventions about how this power is used, especially at the request of the British government. The term peerage can be used both collectively to refer to the entire body of titled nobility, and individually to refer to a specific title. British peerage title holders are termed peers of the Realm.