The Peerage of Ireland refers to the system of nobility in Ireland, which includes titles such as duke, marquess, earl, viscount, and baron. Established in the medieval period, it was formally recognized by the English crown. The peerage played a significant role in Irish society, politics, and land ownership. Unlike the Peerage of England, the Peerage of Ireland has a unique history, particularly after the Act of Union in 1801, which merged the Irish and British parliaments. Today, many titles are still held by descendants of the original peers, although the political power of the peerage has diminished significantly.