The 1841 Census of Ireland was a census that covered the whole island of Ireland. It was conducted as part of the broader 1841 United Kingdom census, which was the first modern census undertaken in the UK. The census is of particular note in Ireland as it was taken shortly before the Great Famine (1845-1852), which resulted in over 1 million deaths and spurred decades of mass emigration. The total population of the island in 1841 was estimated to be just under 8.2 million, which remains the highest recorded population Ireland has ever had. During this year, Ireland also held about 31% of the UK's population. As of the latest censuses – 2022 in the Republic of Ireland and 2021 in Northern Ireland – the island's population stood at just over 7 million, roughly 16% lower than its pre-famine peak.

The Great Famine, also known as the Great Hunger, the Famine and the Irish Potato Famine, was a period of starvation and disease in Ireland lasting from 1845 to 1852 that constituted a historical social crisis and subsequently had a major impact on Irish society and history as a whole. The most severely affected areas were in the western and southern parts of Ireland—where the Irish language was dominant—and hence the period was contemporaneously known in Irish as an Drochshaol, which literally translates to "the bad life" and loosely translates to "the hard times". The worst year of the famine was 1847, which became known as "Black '47". During the Great Hunger, roughly 1 million people died and more than 1 million more fled the country, causing the country's population to fall by 20–25% between 1841 and 1871. Between 1845 and 1855, at least 2.1 million people left Ireland, primarily on packet ships but also on steamboats and barques—one of the greatest exoduses from a single island in history.