John Gustav Thompson
- Bats Unknown, Throws Unknown
- Height 6' 2", Weight 185 lb.
- School Grinnell College, University of Iowa
- Debut August 31, 1903
- Final Game September 21, 1906
- Born June 22, 1877 in Humboldt, IA USA
- Died March 28, 1958 in Kalispell, MT USA
Gus is the only major leaguer through 2019 born in Humboldt, IA, a town in central Iowa. He is one of very few major leaguers who attended Grinnell College in Iowa. In the minors, he spent two years with the Helena Senators and two years in Seattle, among other places.
He came to the majors near the end of the 1903 season with the Pittsburgh Pirates who were on the way to winning the pennant. Manager Fred Clarke had also been born in Iowa. Gus pitched 2 innings in the 1903 World Series. When he came back to the majors with the St. Louis Cardinals in 1906, he pitched much more than he had with the Pirates three years earlier. On a team that lost 98 games, Gus went 2-11.
Gus moved to Kalispell, MT around 1909 with his wife who was from Kalispell, and died there many years later in 1958.  He was called the "father of baseball in Kalispell. He ran a pool hall, a cigar store and a sports bar.