A poor law union was a geographical territory, and early local government unit, in the United Kingdom and Ireland. Poor law unions existed in England and Wales from 1834 to 1930 for the administration of poor relief. Prior to the Poor Law Amendment Act 1834 the administration of the English Poor Laws was the responsibility of the vestries of individual parishes, which varied widely in their size, populations, financial resources, rateable values and requirements. From 1834 the parishes were grouped into unions, jointly responsible for the administration of poor relief in their areas and each governed by a board of guardians. A parish large enough to operate independently of a union was known as a poor law parish. Collectively, poor law unions and poor law parishes were known as poor law districts. The grouping of the parishes into unions caused larger centralised workhouses to be built to replace smaller facilities in each parish. Poor law unions were later used as a basis for the delivery of registration from 1837, and sanitation outside urban areas from 1875. Poor law unions were abolished by the Local Government Act 1929, which transferred responsibility for public assistance to county and county borough councils.
In Ireland the Poor Relief Act of 1838 divided into districts or “unions” in which the local taxable inhabitants were to be financially responsible for all paupers in the area. In 1898 the Poor Law Union was adopted as the basic administrative division in place of the civil parish and barony. Further subdivision into 828 registration districts and 3,751 district electoral divisions followed. Townlands were not arranged according to these divisions with parish and barony retained as a means to make comparisons with records gathered before 1898.