Irish nobility refers to persons who fall into one or more of the following categories of nobility.
- Gaelic nobility of Ireland are those who qualified under the rules of tanistry, or otherwise were descendants in the male line of at least one historical grade of king (Rí). This group includes the descendants of the Norse-Gaelic kings.
- Hiberno-Norman or Old English (Ireland) nobility who were the descendants of the settlers who came to Ireland from Wales, Normandy and England after the Norman invasion of Ireland in 1169–71.
- Peerage of Ireland who owe their titles to those created by the English and later British monarchs of Ireland in their capacity as Lord or King of Ireland.
These groups are not mutually exclusive. There is a some overlap between groups 1 and 2 (prior to the Treaty of Limerick), and a lesser degree of overlap between groups 2 and 3 (prior to the declaration of the Republic of Ireland). Such overlaps may be personal (e.g. a Gaelic noble who was "regranted" his titles by King Henry VIII of England), or they may be geographical (i.e. different noble traditions co-existing in neighbouring parts of the country, which were only distinguished by the date when they finally fell under the Dublin Castle administration).
As a republic, the Irish Constitution precludes the state from conferring titles of nobility, and prevents citizens from accepting titles of nobility or honour - except with the prior approval of the government. While some representatives of clans and familities had obtained "courtesy recognition" as Chiefs of the Name from the Chief Herald of Ireland, this practice was discontinued by 2003 - with the Attorney General noting that such recognitions were unconstitutional and without basis in law. Certain titles are however sometimes used by some people in the Republic of Ireland, and titles are still used and awarded in Northern Ireland - which is part of the United Kingdom of Great Britain and Northern Ireland.