Governor-General Nita Barrow, the country's first female head of state and an international leader in women's rights, died after collapsing at a Christmas party. She was 79.
The cause of her death Tuesday night was not released.
Prime Minister Owen Arthur declared a period of national mourning, in effect until a state funeral Dec. 29. Flags in the Caribbean nation were flown at half-staff.
Arthur called Dame Nita "a citizen of rare and exemplary qualities whose life impacted significantly on this island, on the region and indeed on the world."
A nurse and public health expert, Dame Nita was knighted by Britain's Queen Elizabeth II in 1980 and was appointed Barbados' ambassador to the United Nations in 1986. In 1988, she lost a bitterly contested fight for the presidency of the U.N. General Assembly to Dante Caputo, then Argentina's foreign minister.
Dame Nita was appointed governor general in 1990, serving as Queen Elizabeth's representative to Barbados, an independent member of the Commonwealth.
The sister of the late Prime Minister Errol Barrow, who died in 1987, Dame Nita served on a Commonwealth committee charged with persuading South Africa to abandon apartheid.
In 1985, she convened a series of workshops attended by 11,000 delegates in Nairobi, Kenya, to mark the end of the United Nations' Women's Decade. She also was a president of the World Council of Churches.