William John Posedel (August 2, 1906 – November 28, 1989), nicknamed "Barnacle Bill",[1] was an American right-handed pitcher in Major League Baseball who played for the Brooklyn Dodgers and Boston Bees/Braves in 1938–1941 and in 1946.

He began his professional baseball career in 1929, pitching for the Portland Beavers of the Pacific Coast League.

Posedel's extended service in the PCL resulted in his late Major League debut, at age 31, for the 1938 Dodgers.

In his finest MLB campaign, 1939 with the Boston "Bees" (then the Braves' official nickname), Posedel won 15 of 28 decisions, including five shutouts, for a seventh-place team that claimed only 63 victories all season.

He also worked as a scout for the Pirates (1948), Cleveland Indians (1961) and Kansas City Athletics (1962–1967), and managed the 1957 Beavers from April 29 through the end of the season.