The Fat Man was a popular radio detective drama show that aired in the 1940s and early 1950s. The show was created by Dashiell Hammett, author of The Thin Man. It starred J. Scott Smart as the title character, a detective who started out anonymous but quickly acquired the name "Brad Runyon".

The Fat Man originated on ABC radio in 1946 and ran until 1951. In 1948, it was one of the top 10 shows on Friday nights, with more than six million listeners every week.

The show was on the verge of spinning off into a series of movies with Smart reprising his role of private eye Brad Runyon. However, Hammett ran afoul of the House Un-American Activities Committee.