The Peerage of the United Kingdom is one of the five peerages in the United Kingdom. It comprises most peerages created in the United Kingdom of Great Britain and Ireland after the Acts of Union in 1801, when it replaced the Peerage of Great Britain. New peers continued to be created in the Peerage of Ireland until 1898 (the last creation was the Barony of Curzon of Kedleston).
The House of Lords Act 1999 reformed the House of Lords. Until then, all peers of the United Kingdom were automatically members of the House of Lords. However, from that date, most of the hereditary peers ceased to be members, whereas the life peers retained their seats. All hereditary peers of the first creation (i.e. those for whom a peerage was originally created, as opposed to those who inherited a peerage), and all surviving hereditary peers who had served as Leader of the House of Lords, were offered a life peerage to allow them to continue to sit in the House, should they wish.