Landless Workers' Movement (Portuguese: Movimento dos Trabalhadores Rurais Sem Terra, MST) is a social movement in Brazil, inspired by Marxism, generally regarded as one of the largest in Latin America with an estimated informal membership of 1.5 million across 23 of Brazil's 26 states. MST defines its goals as access to the land for poor workers through land reform in Brazil and activism around social issues that make land ownership more difficult to achieve, such as unequal income distribution, racism, sexism, and media monopolies. MST strives to achieve a self-sustainable way of life for the rural poor.

The MST differs from previous land reform movements in its single-issue focus; land reform for them is a self-justifying cause. The organization maintains that it is legally justified in occupying unproductive land, pointing to the most recent Constitution of Brazil (1988), which contains a passage saying that land should fulfill a social function (Article 5, XXIII). The MST also notes, based on 1996 census statistics, that 3% of the population owns two-thirds of all arable land in Brazil.

In 1991, MST received the Right Livelihood Award "for winning land for landless families and helping them to farm it sustainably."