The former monarch, one of the last surviving World War Two leaders and a cousin of the British Queen Elizabeth II, died at his home in Aubonne in the canton of Vaud on Tuesday, aged 96. He had been suffering from leukaemia.
King Michael reigned over Romania for two periods, from 1927 to 1930, when he was just a young boy, and again from 1940 to 1947.
He is known for ousting fascist ruler Antonescu and ending his country's alliance with the Nazis in 1944, switching sides to the Allies.
However in 1947 he was forced to abdicate and go into exile by the new communist powers. He would not return for several decades.
He married Anne of Bourbon Parma in 1948 after meeting her at the wedding of Queen Elizabeth II and the Duke of Edinburgh in London.
After a spell in the UK where they farmed poultry, the couple moved to Switzerland and brought up their five children.
To make a living the exiled monarch did many jobs including becoming a mechanic and a test pilot.
After the fall of communist dictator Ceausescu in 1989 the new rulers continued to refuse him entry to Romania but he was eventually allowed to return and had his Romanian citizenship restored.
Queen Anne died in Morges in 2016, and King Michael was already too ill to attend her funeral in Romania.
He withdrew from public life last March, handing duties over to his eldest daughter Margareta.