The 1911 census of Ireland was the last census that covered the whole island of Ireland. Censuses were taken at ten-year intervals from 1821 onwards, but the 1921 census was cancelled due to the Irish War of Independence.

Most of the original records of the 1821 to 1851 censuses were destroyed by fire at the Four Courts in Dublin during the Irish Civil War, and those that survive can be searched on the National Archives website. Those of 1861 and 1871 were destroyed soon after collection, and those of 1881 and 1891 were pulped during the First World War.[1] The 20th-century and 21st-century censuses survive in full - the 1901 and 1911 census were put online in 2009 by the National Archives of Ireland, followed on 18 April 2026 by the census of 1926.

The census information was recorded on the following forms:

Form A, which was completed by the head of the family, contained the following information for each person in the home on the night of 2 April:

The form was signed by both the census enumerator and the head of the family.

Form B1, which was known as the House and Building Return, was completed by the enumerator and summarised the following administrative information for the street or townland, or part thereof:

It then summarised the following information pertaining to the houses and families of the street or townland. The information about houses included:

The information about families included: