William Francis Plummer (born March 21, 1947) is an American former professional baseball player. He played in Major League Baseball as a catcher for the Chicago Cubs, Cincinnati Reds and Seattle Mariners. Born in Oakland, California, Plummer attended Anderson Union High School in Anderson, California. He was signed by the St. Louis Cardinals on April 25, 1965 as an amateur free agent. He played three years in the Cardinals' minor league system, then was drafted by the Cubs on November 28, 1967 in the Rule 5 Draft.