Peter O'Toole

Meryl Streep (14)

Katherine Hepburn. She won four Best Leading Actress awards for: Morning Glory (1932/33), Guess Who's Coming To Dinner (1967), The Lion in Winter (1968), and On Golden Pond (1981). The following people have each won exactly three acting Oscars: Ingrid Bergman, Walter Brennan, and Jack Nicholson.

John Ford (4): from 1935 (for "The Informer"), 1940 ("The Grapes Of Wrath"), 1941 ("How Green Was My Valley") and 1952 (for "The Quiet Man")

Beatrice Straight's performance, which lasted 5 minutes and 40 seconds, in Network (1976)

The Return of the King (2003)

They Shoot Horses, Don't They? (1969) with 9 nominations

Ben-Hur (1959), Titanic (1997), and The Return of the King (2003)

Jack Nicholson (12)

Groucho Mark (Honorary Award in 1973 when he was 83 years old).

It Happened One Night (1934), One Flew Over the Cuckoo's Nest (1975), and The Silence of the Lambs (1991)

Tatum O'Neal (age 10) for Paper Moon (1973)

Walt Disney. He won 22 competitive awards and received four honorary awards. He was also nominated for 59 Academy Awards during his lifetime.

Peter Finch for 'Network' (1976) and Heath Ledger for 'The Dark Knight' (2008). Thanks to Marc G for reminding me about Heath Ledger.

GB Shaw, Al Gore. Many Thanks to Diane D for pointing that Al Gore also shares this distinction.

Shirley Temple Black (age 6), who was awarded the inaugural (now retired) non-competitive Academy Juvenile Award in 1934

Cabaret (1972)

Warren Beatty. For "Heaven Can Wait" in 1978 (a remake of 1941's "Here Comes Mr.Jordan" rather than the 1943 "Heaven Can Wait") and for "Reds" in 1981 (for which he won the Best Director award).

All About Eve (1950) and Titanic (1997), both with 14 nominations. All About Eve won 6 awards, and Titanic won 11 awards.

Spencer Tracy (in 1937 and 1938, for "Captains Courageous" and "Boys Town") and Tom Hanks in (1993 and 1994 for "Philadelphia" and "Forrest Gump")

None. The two films which came closest to achieving this feat were A Streetcar Named Desire (1951) and Network (1976), with each film earning three out of the four acting Oscars.

The Turning Point (1977) and The Color Purple (1985). 11 nominations each.

Lina Wertmueller for 'Seven Beauties' in 1976, Jane Campion for 'The Piano' in 1994 and Sofia Coppola for 'Lost in Translation' in 2004 and of course Kathyrn Bigelow who won for The Hurt Locker (2009)

Jessica Tandy (age 80) for Driving Miss Daisy (1989)

Oliver! (1968)

George C Scott (1970 in "Patton") and Marlon Brando (1972 in "The Godfather")