William Pleis III (born August 5, 1937) is a retired American professional baseball player, a left-handed pitcher who appeared in 190 Major League games between 1961 and 1966 for the Minnesota Twins. On April 22, 1961, Pleis notched the Twins' first-ever win in their new home state and home field, Metropolitan Stadium. Pleis retired from pitching after the 1968 season. He allowed 269 hits and 127 bases on balls in 280+2⁄3 innings pitched in the Majors, with 184 strikeouts, 13 saves and one complete game.