| Jack Janssen | |
| Order1: | Member of the Kansas State Senate from the 35th District |
| Term Start1: | 1973 |
| Term End1: | 1980 |
| Successor1: | Roy Ehrlich |
| Order2: | Member of the Kansas State Senate from the 23rd District |
| Term Start2: | 1969 |
| Term End2: | 1972 |
| Order3: | Member of the Kansas State Senate from the 33rd District |
| Term Start3: | 1965 |
| Term End3: | 1968 |
| Birth Date: | 1923 7, mf=yes[1] |
| Birth Place: | Lyons, Kansas |
| Death Place: | Lyons, Kansas |
| Party: | Democrat |
| Spouse: | Dorothy Link (m. August 14, 1943) |
| Residence: | Lyons, Kansas |
Jack Wesley Janssen (July 6, 1923 - March 7, 2013) was an American politician who served as a Democrat in the Kansas State Senate from 1965 to 1980.
Janssen was born and resided in Lyons, Kansas. He was elected to the Kansas State Senate in 1964 and served for four terms: first in the 33rd District, followed by one term in the 23rd District, and two final terms in the 35th District.