The hereditary peers form part of the peerage in the United Kingdom. As of April 2023, there are 806 hereditary peers: 30 dukes (including six royal dukes), 34 marquesses, 189 earls, 110 viscounts, and 443 barons (not counting subsidiary titles).
Not all hereditary titles are titles of the peerage. For instance, baronets and baronetesses may pass on their titles, but they are not peers. Conversely, the holder of a non-hereditary title may belong to the peerage, as with life peers. Peerages may be created by means of letters patent, but the granting of new hereditary peerages has largely dwindled; only seven hereditary peerages have been created since 1965, four of them for members of the British royal family.
As a result of the Peerage Act 1963 all peers except those in the peerage of Ireland were entitled to sit in the House of Lords, but since the House of Lords Act 1999 came into force only 92 hereditary peers, elected by and from all hereditary peers, are permitted to do so, unless they are also life peers. Peers are called to the House of Lords with a writ of summons.
The hereditary peerage, as it now exists, combines several different English institutions with analogues from Scotland and Ireland.
English earls are an Anglo-Saxon institution. Around 1014, England was divided into shires or counties, largely to defend against the Danes; each shire was led by a local great man, called an earl; the same man could be earl of several shires. When the Normans conquered England, they continued to appoint earls, but not for all counties; the administrative head of the county became the sheriff. Earldoms began as offices, with a perquisite of a share of the legal fees in the county; they gradually became honours, with a stipend of £20 a year. Like most feudal offices, earldoms were inherited, but the kings frequently asked earls to resign or exchange earldoms. Usually there were few earls in England, and they were men of great wealth in the shire from which they held title, or an adjacent one, but it depended on circumstances: during the civil war between Stephen and the Empress Matilda, nine earls were created in three years.