The Lancaster House Agreement, signed on 21 December 1979, declared a ceasefire, ending the Rhodesian Bush War; and directly led to Rhodesia achieving internationally recognised independence as Zimbabwe. It required the full resumption of direct British rule, nullifying the Unilateral Declaration of Independence of 1965. British governance would be strictly prescribed to the duration of a proposed election period followed by a formal power transfer back to a recognised, sovereign state. Constitutional instruments would thus be transferred from the British state to a popularly elected government, under an unqualified universal franchise vote. Crucially, the political wings of the black nationalist groups ZANU and ZAPU, who had been waging an increasingly violent insurgency, would be permitted to stand candidates in the forthcoming elections. This was however conditional to compliance with the ceasefire and the verified absence of voter intimidation.

The Agreement would lead to the dissolution of the unrecognised state of Zimbabwe Rhodesia, created months earlier by the Internal Settlement; an agreement forged between moderate black nationalists and Prime Minister Ian Smith's Government. While Zimbabwe Rhodesia remained unrecognised, the Internal Settlement enfranchised the majority of blacks (hitherto the key British demand) and resulted in the election of the country's first black Prime Minister, Bishop Abel Muzorewa.

Lancaster House covered the Independence Constitution, pre-independence arrangements and the terms of ceasefire. The Agreement is named after Lancaster House in London, where the conference on independence from 10 September to 15 December 1979 was held.

The parties represented during the conference were: the British Government, the Patriotic Front led by Robert Mugabe and Joshua Nkomo, ZAPU (Zimbabwe African Peoples Union) and ZANU (Zimbabwe African National Union) and the Zimbabwe Rhodesia Government, represented by Prime Minister, Bishop Abel Muzorewa and Ian Smith, Minister without Portfolio.