Kenneth MacMillan was born in Dunfermline, Scotland in 1929 and grew up in Great Yarmouth where he took his first ballet lessons with Phyllis Adams. In 1945, he began his studies on a scholarship at Sadler’s Wells School (now the The Royal Ballet School) where he studied with Ninette de Valois and Vera Volkova.
In 1946, MacMillan joined the newly formed Sadler's Wells Theatre Ballet (SWTB) and in 1948 was promoted to the Sadler’s Wells Ballet at Covent Garden. He returned to the SWTB in 1952 and began choreographing for their new choreographic group. His first ballet, Somnambulism, set to a symphonic jazz score by Stan Kenton, was the hit of the SWTB’s first Sunday evening performance on February 1, 1953. Thereafter, MacMillan’s ballets ranged from abstract works of pure dance to large-scale company works, including The Rite of Spring, Romeo and Juliet and Song of the Earth.
From 1966 to 1969, MacMillan worked as Director of Deutsche Oper Berlin, staging The Sleeping Beauty and Swan Lake as well as making short ballets, including the one-act version of Anastasia. In 1970, he returned to London as Director of The Royal Ballet, succeeding Sir Frederick Ashton.
From 1984 to 1989, MacMillan was the Associate Director of American Ballet Theatre, staging many of the works in the company’s repertoire. He was also the Artistic Associate of Houston Ballet and staged Manon for the company’s 1992/93 season.
MacMillan died on October 29, 1992 during a performance of his ballet Mayerling at the Royal Opera House, Covent Garden. Until his sudden death, he continued to work for The Royal Ballet as the company's Principal Choreographer. In 1996, MacMillan was posthumously awarded The Vaslav Nijinsky Medal.