Frederick William "Fritz" Clausen (April 26, 1869 – February 11, 1960) was a professional baseball pitcher in Major League Baseball who played between 1892 and 1896 for the Louisville Colonels, and Chicago Colts. Clausen batted right-handed and threw left-handed. He was born in New York City.

In a four-season career, Clausen posted a 16–22 record with 134 strikeouts and a 3.58 ERA in 324⅓ innings pitched, including 36 complete games and two shutouts.

Clausen died from injuries suffered in an accidental fall in Memphis, Tennessee, at the age of 90.

• Career statistics from ESPN, or Baseball Reference, or Fangraphs, or Baseball Reference (Minors)