COLOMBO, Sri Lanka — Sirimavo Bandaranaike, who became the world's first woman prime minister when she was elected head of Sri Lanka's government four decades ago, retired from office Thursday at the age of 84.

Bandaranaike, a dominant force in Sri Lankan politics, served three terms as prime minister and is the mother of Sri Lankan President Chandrika Kumaratunga. Even during her most recent term, in an era when the country's prime ministership is mostly a ceremonial post, she wielded enormous power.

But Bandaranaike has been in poor health for months, and she stepped down to let her daughter reorganize the Cabinet ahead of elections. A stunned parliament was told Thursday that her post will be filled by Ratnasiri Wickramanayaka, the country's minister of public administration and home affairs.

The resignation appears to end a four-decade run of victory, disgrace and redemption for a woman who took power six years before Indira Gandhi became India's first woman prime minister. The election of a woman head of government was so unusual on July 20, 1960, that newspapers weren't sure what to call her.

"There will be need for a new word. Presumably, we shall have to call her a Stateswoman," London's Evening News wrote the next day. "This is the suffragette's dream come true."

Born Sirimavo Ratwatte on April 17, 1916, Bandaranaike was a member of one of this Indian Ocean island's wealthiest families. In 1940 she married Soloman Dias Bandaranaike, a senior politician in the United National Party that was governing Sri Lanka, then called Ceylon.

After breaking away to form his own Sri Lanka Freedom Party, her husband was elected prime minister in 1956. A deranged Buddhist monk assassinated him three years later.

After a period of mourning, Bandaranaike transformed from a shy housewife to a political dynamo: She campaigned for her husband's party in the 1960 elections and became party leader in May of that year.

In her first speech after winning election she addressed the women of Sri Lanka, saying, "My victory is really their victory." And at the Commonwealth Prime Ministers Conference in London in March 1961, Bandaranaike became the first woman to sit at the conference table among some of the world's most eminent statesmen.

She governed until 1965, lost the next election, then regained power in 1970.

"She knew her priorities very well and had foresight," said Jehan Perera, a Sri Lankan political analyst. "She knew keeping good relations with big neighbor India was very crucial for a small country like ours."

Despite her wealth and her party's rightist tradition, Bandaranaike began shifting toward more leftist policies. She became influenced by strong personal ties with China and with Indira Gandhi, her Indian counterpart.

"She and the late Mrs. Gandhi had a personal rapport. Both had some similarities, like losing their husbands at young age and coming from top class families," Perera said.

As part of her Cold War shift toward the Soviet bloc, Bandaranaike ordered the U.S. Peace Corps out of Sri Lanka in 1970 and closed the Israeli Embassy. Two years later she made the country a republic.

During that term she also nationalized private companies and church schools. Imports were banned. Many Sri Lankans still remember the long queues for bread and rationing of basic necessities such as rice and cloth.

She used the military to ruthlessly crush a 1971 insurrection by Marxist rebels, killing as many as 20,000 people. The small Marxist parties who were part of her coalition government began to desert her.

Bandaranaike's unpopularity grew when she nationalized the country's largest newspaper groups and postponed elections for two years. When they were finally held in 1977, her party was reduced to a mere eight seats in the 157-member Parliament, down from 90 in 1970.

Bandaranaike managed to keep her own seat from her hometown, Attanagalla, 20 miles northeast of the capital, Colombo. But in 1980 parliament expelled her, accusing her of misusing power while prime minister, and banned her from public office for seven years. Her civic rights were restored in 1986.

Suffering from diabetes and a foot problem that eventually put her in a wheelchair, Bandaranaike reduced her political activities. In 1993 Kumaratunga took over the party's leadership, and when she was elected president a year later, she appointed her trusted mother to the prime minister's post.

Bandaranaike's successor, Wickramanayaka, is expected to shore up support for Kumaratunga among powerful Buddhist clergy who violently opposed her plan to give autonomy to minority ethnic Tamils in Sri Lanka's north. Tamils accuse the government of widespread discrimination in education and jobs, and Tamil rebels have fought a 17-year war that has cost more than 62,000 lives.