Mr Ustinov, a renaissance man whose talents included writing plays, movies and novels as well as directing operas, also devoted himself to the world's children for more than 30 years as a goodwill ambassador for Unicef.
He died of heart failure on Sunday night in a clinic near his home at Bursins overlooking Lake Geneva, said close friend Leon Davico, a former Unicef spokesman.
"He was a unique person, someone you could really count on," said Mr Davico.
Born in London on April 16, 1921, the only son of a Russian artist mother and a journalist father, Mr Ustinov claimed also to have Swiss, Ethiopian, Italian and French blood everything except English.
He was as he noted proudly in his autobiography Dear Me conceived in St Petersburg, Russia, baptised in a village near Stuttgart, Germany, and reared under a succession of Cameroonian, Irish and German nurses.
His imposing figure, variously described as resembling a teddy bear, a giant panda or a Georgian frontage, began 12lbs at birth and stayed with him throughout his career.
Ustinov made some 90 films and his narration of Tchaikovsky's Peter and the Wolf won him a Grammy.
Among his film roles were a nomad who befriends a family in The Sundowners, Agatha Christie's Belgian detective Hercule Poirot in Death on the Nile, and Abdi Aga, an illiterate tyrant with pretensions of learning in Memed My Hawk.
He won Oscars for the role of Batiatus, owner of the gladiator school in Spartacus (1960), and as Arthur Simpson, an English small-time black marketeer in Turkey who gets caught up in a jewel heist in Topkapi (1965).
His Nero won him a Golden Globe for best supporting actor in the 1951 film Quo Vadis. He also won three television Emmys.
He was performing by the time he was three, mimicking politicians of the day when his parents invited Ethiopian Emperor Haile Selassie for dinner.
He was educated at the prestigious Westminster School, but hated it. He left at 16, appeared in his first revue and had his first stage play presented in London in 1940, when he was 19.
He turned producer at 21 when he presented Squaring the Circle shortly before he entered the British army in 1942.
He later became a staunch advocate for Unesco, the United Nations Educational, Scientific and Cultural Organisation. "He never said no to anything the United Nations asked him to do," Mr Davico said.
His long service as a UN goodwill ambassador led Secretary-General Kofi Annan to joke he was the man to take over from him.
He remained active until close to his death, playing himself in the 2003 TV movie Winter Solstice.
Mr Ustinov was married three times, and is survived by his four children and his third wife.