From 1845 to 1852, as Britain secured a place as the world's largest and most powerful industrial empire, Ireland starved. The Great Famine fractured British confidence in long-held assumptions about political economy, 'civilisation' and freedom and raised a spectre of disorder in Britain itself. The Irish Question shows where Ireland stood in the British empire, and tells both the horrific story of the Famine and the long history of Ireland as a laboratory for colonialism and imperial rule elsewhere in the empire. Britain and Ireland are friends, enemies, intimates, and strangers to each other. In the mid-nineteenth century, as Britain stood secure in its place as the world's most powerful empire, a terrible famine in Ireland revealed the contradictions and violence at the heart of British imperialism. The Irish Question is a new history of the Great Famine (1845-52) in both the United Kingdom and the wider world, revealing the place of Ireland and the Irish in British politics, economics, culture, and ecology. Ideas about labour, 'civilisation' and freedom developed by administrators, clerics, scientists, and writers in Ireland became templates for British rule around the empire. The Irish Question is a history of suffering - of bad policy, bad harvests and bad luck that tore a hole in Britain's power and self-regard and Ireland's people, politics, and culture. It is also a timely reminder of the fundamentally imperial character of the United Kingdom. As the UK shudders after Brexit and the COVID-19 pandemic, Ireland's ties to the UK are dissolving. The Irish Question shows, with new research and broad synthesis, the fraught and complex connections that held the two islands together - and pulled them apart. Ireland, conquered, lost, and reconquered by Anglo-Saxon and Tudor kings of England, by Oliver Cromwell's English Commonwealth, and finally absorbed into a new United Kingdom under the 1800 and 1801 Acts of Union, was both England's first overseas colony, exploited and oppressed, and a font of military, intellectual and cultural manpower and talent for the British empire, entangled in the rapid growth of British power in the eighteenth and nineteenth centuries. From 1845 to 1852, the failure of potato crops in Ireland caused the most devastating famine in the history of the United Kingdom. At least a million people died, of starvation and disease. As many as two million left Ireland - for England, for North America, for Australia and elsewhere. In Britain, the famine was more than a humanitarian or imperial crisis. Since the eighteenth century, Ireland had been a laboratory for English, and then British, ideas about land, labour, freedom, and 'civilisation.' When British liberals looked to Ireland, they were confounded by a place and a people that seemed to put the lie to the certainties of political economy, and that seemed to threaten to upend the 'civilisation' that Britain promised to the empire it ruled. Irish peasants, living on tiny farms distributed according to a complex system of land use and hereditary rights and obligations, frustrated and fascinated British political economists and travellers, for whom the peat bogs and 'lazy bed' potato fields seemed to cry out for improvement and Enlightenment. Catholicism, the religion practised by most of Ireland's cottiers and by many of its most powerful landlords, was anathema in Britain, symbolic of the threat posed by France and Spain to British power. Irish agricultural workers were alien to emerging English ideas about capitalism and civilisation, able to survive and multiply despite what seemed to English eyes to be a bone-deep fecklessness in their attitude to labour. At the same time, Irish workers were restive and rebellious; in Ireland, Britain first experimented with a style of centralised, paramilitary policing that would prove useful against colonised people throughout the empire. When Catholics, denied civil rights in Britain for centuries, were restored to full citizenship in 1829, the 'Catholic Emancipation' threw into sharp relief debates about the meaning of political and economic freedom within Britain - questions that would only become more urgent as Britain expanded the franchise and ended colonial slavery in the years to come. When the Great Famine struck, the contradictions and violence of Britain's imperial project were laid bare.