Below is a chronological listing of the United States senators from Idaho. The state was admitted to the Union on July 3, 1890, and its U.S. senators belong to class 2 and class 3. Idaho's current U.S. Senators are Republicans Mike Crapo (serving since 1999) and Jim Risch (serving since 2009). William Borah was Idaho's longest-serving senator (1907–1940). Idaho is one of fifteen states alongside Arizona, Colorado, Florida, Georgia, Hawaii, Indiana, Louisiana, Maine, Massachusetts, Minnesota, Missouri, Nevada, South Dakota and Utah to have a younger senior senator and an older junior senator.

List of senators

! rowspan=6 | 1 ! 1 ! rowspan=3 | 2 ! rowspan=4 | 3 ! rowspan=4 | 2 ! rowspan=5 | 4 ! rowspan=25 | 3 ! 5 ! rowspan=4 | 6 ! rowspan=2 | 7 ! rowspan=5 | 8 ! rowspan=3 | 9 ! rowspan=3 | 10 ! rowspan=5 | 11 ! rowspan=4 | 4 ! rowspan=8 | 12 ! 5 ! rowspan=2 | 6 ! 7 ! rowspan=7 | 8 ! rowspan=3 | 13 ! rowspan=14 | 14 ! rowspan=6 | 9 ! rowspan=9 | 10 ! rowspan=6 | 15 ! rowspan=9 | 11 ! rowspan=3 | 16 ! rowspan=15 | 17 ! rowspan=9 | 12