Sanitary districts were established in England and Wales in 1875 and in Ireland in 1878. The districts were of two types, based on existing structures:

Each district was governed by a sanitary authority and was responsible for various public health matters such as providing clean drinking water, sewers, street cleaning, and clearing slum housing.

In England and Wales, both rural and urban sanitary districts were replaced in 1894 by the Local Government Act 1894 by the more general rural districts and urban districts. A similar reform was carried out in Ireland in 1899 by the Local Government (Ireland) Act 1898.

Sanitary districts were formed under the terms of the Public Health Acts 1873 and 1875. Instead of creating new divisions, existing authorities were given additional responsibilities.

Urban sanitary districts were formed in any municipal borough governed under the Municipal Corporations Act 1835, in any Improvement Commissioners District formed by private act of parliament, and in any Local Government District formed under the Public Health Act 1848 or Local Government Act 1858.