The Land War (Irish: Cogadh na Talún) was a period of agrarian agitation in rural Ireland (then wholly part of the United Kingdom) 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.
From 1870, various governments introduced a series of Land Acts that granted many of the activists' demands. William O'Brien played a leading role in the 1902 Land Conference to pave the way for the most advanced social legislation in Ireland since the Union, the Land Purchase (Ireland) Act 1903. This Act set the conditions for the break-up of large estates by government-sponsored purchase.