She is survived by her husband, Edinburgh-born veteran broadcaster Ludovic Kennedy, whom she married in 1950.
Born Moira King in Dunfermline in 1926, the actress danced ballet from the age of six and made her international debut with the International Ballet at 15.
She joined the Sadler's Wells aged 16 and entered films as the ballerina star of the 1948 film The Red Shoes and Tales of Hoffman (1951). She also appeared on the London stage.
In recent years Lady Kennedy reviewed books for a national newspaper and went on to write two books of her own.
The dancer was born and grew up in Barum House in Dunfermline, which was built for her grandfather James Shearer, in 1880.
In 2000 the size-three satin pair of red ballet shoes worn by the actress in The Red Shoes were sold for 14,100 at auction.
The film, made by the veteran movie duo Powell and Pressburger, is still considered one of the greats of British cinema, and was nominated for four Oscars.
Her nephew is Richard Calvocoressi, Director of the Scottish National Gallery of Modern Art.