William R. Seinsoth (April 4, 1947 – September 7, 1969) was a first baseman who is most notable for winning the 1968 College World Series Most Outstanding Player award while a junior at University of Southern California. He is one of seven players from University of Southern California to win that award. The others are Bill Thom, Bud Hollowell, Russ McQueen, George Milke, Rod Boxberger and Wes Rachels. Also an All-American, he hit .327 with 31 RBI in his sophomore season. The next year, he hit .312 with six home runs and 23 RBI. He hit .368 with 14 home runs and 52 RBI in 1969. He had a career .337 average in college.