William Peter Filson (born September 28, 1958) is a retired Major League Baseball pitcher. He played during seven seasons at the major league level for the Minnesota Twins, Chicago White Sox, New York Yankees, and Kansas City Royals.

Filson attended Temple University, and in 1977 and 1978 he played collegiate summer baseball with the Hyannis Mets of the Cape Cod Baseball League.^[1] He was selected by the Yankees in the 9th round of the 1979 MLB Draft.^[2]

Filson played his first professional season with their Rookie league Paintsville Yankees and Class-A (Short Season) Oneonta Yankees in 1979, and split his last between Kansas City and their Triple-A Omaha Royals in 1990. Filson can be seen delivering a single pitch as a Royal in the Ken Burns documentary Baseball, at the beginning of the section entitled "Extra Innings."

He was dealt along with Larry Milbourne and John Pacella from the Yankees to the Twins for Butch Wynegar and Roger Erickson on May 12, 1982.^[3]

With the Twins, Filson was affectionately nicknamed "Freeze".^[4]

In 2003 Filson was hired as pitching coach for the Newark Bears of the independent Atlantic League, Filson remained with the team until 2006.

Filson is currently a pitching instructor at AFC Baseball in Bala Cynwyd, Pennsylvania, where he provides instruction to players at Harriton High School, Radnor High School, the Chester County Crawdads, and Wayne Wolverines.