Marion Ladewig (née Van Oosten; October 30, 1914 – April 16, 2010) was an American ten-pin bowler.
She was named Female Bowler of the Year by the Bowling Writers Association of America a record nine times between 1950 and 1963 (1950–54, '57–'59, '63).
A Grand Rapids, MI native, Ladewig is the only woman to win WIBC City, State, and National All-Events titles in the same year (1951).
She is the all-time leader in U.S. Women's Open championships with eight; the next closest bowler is Liz Johnson with six.
Ladewig also won the Women's World Invitational tournament five times (1957, '60, '62, '63 and '64)[1] and the inaugural PWBA Championship in 1960.