The Highland Potato Famine (Scottish Gaelic: Gaiseadh a' bhuntàta) was a period of 19th century Highland and Scottish history (1846 to roughly 1856) over which the agricultural communities of the Hebrides and the western Gàidhealtachd (Scottish Highlands) saw their potato crop (upon which they had become over-reliant) repeatedly devastated by potato blight. It was part of the wider food crisis facing Northern Europe caused by potato blight during the mid-1840s, whose most famous manifestation is the Great Irish Famine, but compared to its Irish counterpart it was much less extensive (the population at risk was never more than 200,000) and took many fewer lives (prompt and major charitable efforts by the rest of the United Kingdom ensured that there was relatively little starvation). The terms on which charitable relief was given, however, led to destitution and malnutrition amongst its recipients. A government enquiry could suggest no short-term solution other than reduction of the population of the area at risk by emigration to Canada or Australia. Highland landlords organised the emigration of about 16,000 of their tenants (chiefly to Canada); many Gaels made their own way to other destinations in the Scottish Lowlands or further afield and it is estimated that about a third of the population of the western Scottish Highlands (about 90,000) emigrated between 1841 and 1861.
Over the 18th century, Gaelic society had changed greatly. On the southern and eastern fringes of the Highlands, most arable land was divided into family farms with 20 to 50 acres employing crofters (with some land held in their own right, insufficient on its own to give them an adequate living) and cottars (farm workers with no land of their own, sometimes sub-let a small patch of land by their employer or a crofter). The economy had become assimilated to that of the Lowlands, whose proximity allowed and encouraged a diverse agriculture. Proximity to the Lowlands had also led to a steady drain of population from these areas. In the Western Isles and the adjacent mainland developments had been very different. Chieftains become "improving" landlords had found sheep-grazing to be the most remunerative form of agriculture; to accommodate this they had moved their tenants to coastal townships where they hoped valuable industries could be developed and established an extensive crofting system (see Highland Clearances). Croft sizes were set low to encourage the tenantry to participate in the industry (e.g. fishing, kelp ) the landlord wished to develop. A contemporary writer thought that a crofter would have to do work away from his holding for 200 days a year if his family were to avoid destitution. The various industries the crofting townships were supposed to support mostly prospered in the first quarter of the 19th century (drawing workers over and above the originally intended population of townships) but declined or collapsed over its second quarter. The crofting areas were correspondingly impoverished, but able to sustain themselves by a much greater reliance on potatoes (it was reckoned that one acre growing potatoes could support as many people as four acres growing oats). Between 1801 and 1841 the population in the crofting area increased by over half, whereas in the eastern and southern Highlands the increase in the same period was under 10 percent. Consequently, immediately pre-blight, whilst mainland Argyll had over two acres of arable land per inhabitant, there was only half an acre of arable land per head in Skye and Wester Ross: in the crofting area, as in Ireland, the population had grown to levels which only a successful potato harvest could support.