Answer:
Not counting honorary recipients, a total of 24 Oscar winners have hosted or co-hosted the Academy Awards. The list includes: Lionel Barrymore (1932), Frank Capra (1936), James Stewart (1946, 1958), Fredric March (1954), Claudette Colbert (1956), Joseph L. Mankiewicz (1956), Celeste Holm (1957), David Niven (1958, 1958 and 1974), Jack Lemmon (1958, 1964 and 1972), Sir Laurence Olivier (1959), Frank Sinatra (1963, 1975), Helen Hayes (1972), Sir Michael Caine (1973), Charlton Heston (1973), John Huston (1974), Shirley MacLaine (1975), Goldie Hawn (1976, 1987), Ellen Burstyn (1977), Warren Beatty (1977), Jane Fonda (1977, 1986), Liza Minnelli (1983), Walter Matthau (1976, 1983), Robin Williams (1986) and Whoopi Goldberg (1994, 1996, 1999 and 2002).