The Great Famine was a period of mass starvation, disease and emigration in Ireland between 1845 and 1852. It is sometimes referred to, mostly outside Ireland, as the Irish Potato Famine because about two-fifths of the population was solely reliant on this cheap crop for a number of historical reasons. During the famine approximately 1 million people died and a million more emigrated from Ireland, causing the island's population to fall by between 20% and 25%.
The proximate cause of famine was a potato disease commonly known as potato blight, which ravaged potato crops throughout Europe during the 1840s. However the impact in Ireland was disproportionate as one third of the population was dependent on the potato for a range of ethnic, religious, political, social and economic reasons, such as land acquisition, absentee landlords and the Corn Laws, which all contributed to the disaster to varying degrees and remain the subject of intense historical debate.
Although the potato crop failed, the country itself was still producing and exporting large quantities of food. Ireland exported approximately thirty to fifty shiploads per day to Britain, which was more than enough to feed the population. The food exports in conjunction with draconian laws have led some historians and authors to use the term genocide in relation to the tragedy.
The famine was a watershed in the history of Ireland. Its effects permanently changed the island's demographic, political and cultural landscape. For both the native Irish and those in the resulting diaspora, the famine entered folk memory and became a rallying point for various Home rule and United Ireland movements, as the whole island was then part of the United Kingdom of Great Britain and Ireland.
The massive famine soured the already strained relations between many of the Irish people and the British Crown, heightening Irish republicanism, which eventually led to Irish independence in the next century. Modern historians regard it as a dividing line in the Irish historical narrative, referring to the preceding period of Irish history as "pre-Famine".
It is not known exactly how many people died during the period of the famine, although it is believed more died from diseases than from starvation. State registration of births, marriages or deaths had not yet begun, and records kept by the Roman Catholic Church are incomplete. One possible estimate has been reached by comparing the expected population with the eventual numbers in the 1850s. A census taken in 1841 recorded a population of 8,175,124. A census immediately after the famine in 1851 counted 6,552,385, a drop of over 1.5 million in 10 years. The census commissioners estimated that at the normal rate of increase the population in 1851 should have been just over 9 million.
In 1851, the census commissioners collected information on the number who died in each family since 1841, the cause, season and year of death. They recorded 21,770 total deaths from starvation in the previous decade, and 400,720 deaths from disease. Listed diseases were fever, dysentery, cholera, smallpox and influenza; the first two being the main killers (222,021 and 93,232). The commissioners acknowledged that their figures were incomplete and that the true number of deaths was probably higher: "The greater the amount of destitution of mortality ... the less will be the amount of recorded deaths derived through any household form; – for not only were whole families swept away by disease ... but whole villages were effaced from off the land." Later historians agree that the 1851 death tables "were flawed and probably under-estimated the level of mortality". The combination of institutional and figures provided by individuals gives "an incomplete and biased count" of fatalities during the famine. Cormac Ó Gráda referencing the work of W. A. MacArthur, writes that specialists have long known the Irish death tables were inaccurate. As a result, Ó Gráda says that the tables undercount the number of deaths, because information was gathered from surviving householders having to look back over the previous 10 years, and death and emigration had cleared away entire families, leaving few or no survivors to answer the census questions.
While the famine was responsible for a significant increase in emigration from Ireland, of anywhere from 45% to nearly 85% depending on the year and the county, it was not the sole cause. Nor was it even the era when mass emigration from Ireland commenced. That can be traced to the middle of the 18th century, when some 250,000 people left Ireland over a period of 50 years to settle in the New World. From the defeat of Napoleon to the beginning of the famine, a period of 30 years, "at least 1,000,000 and possibly 1,500,000 emigrated". However, during the worst of the famine, emigration reached somewhere around 250,000 in one year alone, with far more emigrants leaving from western Ireland than any other part.
Families did not migrate en masse but younger members of families did – so much so that emigration almost became a rite of passage, as evidenced by the data that show that, unlike similar emigration throughout world history, women emigrated just as often, just as early, and in the same numbers as men. The emigrant started a new life in a new land, sent remittances "£1,404,000 by 1851" back to his/her family in Ireland which, in turn, allowed another member of the family to emigrate.
The potato remained Ireland's staple crop after the famine; at the end of the 19th century, the Irish per capita consumption of four pounds a day was the highest in the world. Later famines made only minimal effect and are generally forgotten, except by historians. By the 1911 census, the island of Ireland's population had fallen to 4.4 million, about the same as the population in 1800 and 2000 and only a half of its peak population.
On the other hand, the population of England and Wales doubled from 16 million in 1841 to 32.5 million in 1901.
The Famine gave considerable impetus to the shift from Irish to English as the language of the majority. Those most gravely affected by the Famine were mostly in Irish-speaking districts, and those districts also supplied most of the emigrants. Awareness of the cultural loss provided a spur to the work of Irish language activists in Ireland, Britain, America and Australia, resulting in the foundation of such organisations as the Gaelic League.
Ireland's mean age of marriage in 1830 was 23.8 for women and 27.47 for men where they had once been 21 for women and 25 for men, respectively, and those who never married numbered about 10% of the population; in 1840, they had respectively risen to 24.4 and 27.7; in the decades after the Famine, the age of marriage had risen to 28–29 for women and 33 for men and as many as a third of Irishmen and a fourth of Irishwomen never married due to low wages and chronic economic problems that discouraged early and universal marriage.