The Land War was a period of agrarian agitation in rural Ireland that began in 1879. It may refer specifically to the first and most intense period of agitation between 1879 and 1882, or include later outbreaks of agitation that periodically reignited until 1923, especially the 1886–1891 Plan of Campaign and the 1906–1909 Ranch War. The agitation was led by the Irish National Land League and its successors, the Irish National League and the United Irish League, and aimed to secure fair rent, free sale, and fixity of tenure for tenant farmers and ultimately peasant proprietorship of the land they worked.

Ireland was part of the United Kingdom from 1801 to 1922. For almost all of this period, the island was governed by the UK Parliament in London through its Dublin Castle administration in Ireland. Ireland underwent considerable difficulties in the 19th century, especially the Great Famine of the 1840s which started a population decline that continued for almost a century. The late 19th and early 20th centuries saw a vigorous campaign for Irish Home Rule. While legislation enabling Irish Home Rule was eventually passed, militant and armed opposition from Irish unionists, particularly in Ulster, opposed it. Proclamation was shelved for the duration following the outbreak of World War I. By 1918, however, moderate Irish nationalism had been eclipsed by militant republican separatism. In 1919, war broke out between republican separatists and British Government forces. Subsequent negotiations between Sinn Féin, the major Irish party, and the UK government led to the signing of the Anglo-Irish Treaty, which resulted in five-sixths of the island seceding from the United Kingdom, becoming the Irish Free State, with only the six northeastern counties remaining within the United Kingdom.