Stig Kjell Olof (Ola) Ullsten (born 23 June 1931) is a Swedish former politician and diplomat who was Prime Minister of Sweden from 1978 to 1979 and leader of the Liberal People's Party from 1978 to 1983. He also served as Deputy Prime Minister briefly in 1978 and then again from 1980 to 1982 and served as Minister for Foreign Affairs from 1979 to 1982.