DUBLIN -- Sean MacBride, 83, an international jurist, crusader for human rights and the only person to win both the Nobel and Lenin peace prizes, died of pneumonia Jan. 15 at his home here.

Mr. MacBride was an Irish Republican Army guerrilla leader in his teens and he went on to become a cofounder of the human rights group Amnesty International.

The nuclear disarmament advocate and one-time assistant secretary general of the United Nations also was one of Ireland's most noted constitutional and criminal lawyers. He returned to his Dublin law practice in 1979 after a 20-year hiatus espousing worldwide issues.

In 1974, he shared the Nobel Prize with Eisaku Sato, former prime minister of Japan. Mr. MacBride was cited for his many years of human rights work with Amnesty International and the International Jurist Commission.

Three years later, the Soviet Union awarded him the Lenin International Prize for Peace for his work in South-West Africa, or Namibia. He was among only a few Westerners to be given the award from a Soviet government-approved committee.

Mr. MacBride campaigned to make the cause of Namibian independence from South Africa an international issue, but failed to persuade Pretoria to yield control of the mineral-rich territory.

Amnesty International, which he helped found in 1961, won the 1977 Nobel Peace Prize for its campaign on behalf of political prisoners around the world.

Mr. MacBride was the chief sponsor of a 1984 antidiscrimination code known as the MacBride Principles that is aimed at forcing U.S. companies operating in Northern Ireland to ensure equal employment opportunities for Roman Catholics.

Born in Paris, where his parents were living in exile, Mr. MacBride grew up among European intellectuals and nationalists in Paris, London and Dublin.

His father, Maj. John MacBride, was a leader of the ill-fated 1916 Easter Rising in Dublin. John MacBride was executed, along with his brother, Joseph, by the British.

His mother, Maud Gonne MacBride, rebel daughter of an English army colonel, was repeatedly jailed for her nationalist activities.

Mr. MacBride was leading his own IRA unit when he was 16. When civil war broke out between IRA factions over the 1921 peace treaty that divided Ireland, he fought with the IRA's militant antipartitionists, forerunners of the Provisional IRA still fighting to drive the British out of Northern Ireland.

Mr. MacBride left the movement when Eamon DeValera, a 1916 hero, dropped the oath of allegiance to the British crown from the Irish Free State's 1937 constitution.

Mr. MacBride often defended IRA suspects and fought antiterrorist legislation, but he strongly opposed the IRA's current campaign of violence.

His nationalism established his credentials in the Third World, whose future leaders he had met in the 1920s at anti-imperialist conferences. Among them were Ho Chi Minh and Pandit Nehru.

In 1946, Mr. MacBride founded a radical nationalist party, Clann na Poblachta, which two years later helped oust De Valera's Fianna Fail Party from 16 years in power. He became a foreign minister in the 1948-51 coalition government. His party collapsed in 1965.

During the Vietnam War, he won disfavor in Washington when he carried a message from Pope Paul VI to Hanoi and denounced the U.S. bombing campaign.

The distrust continued into 1979, when Mr. MacBride made an abortive attempt to break the deadlock between Iran and the United States over the holding of American hostages at the U.S. Embassy in Tehran. The mission failed because he insisted Washington acknowledge atrocities under Shah Mohammed Reza Pahlavi.

In 1977, he tried without success to negotiate a cease-fire between the IRA and Protestant paramilitary groups in Northern Ireland.

His Argentine-born wife, Catalina, died in 1976. He is survived by one son and one daughter.