This is a complete list of United States senators during the 114th United States Congress listed by seniority from January 3, 2015, to January 3, 2017.
In this Congress, Barbara Boxer (D-California) was the most senior junior senator and Deb Fischer (R-Nebraska) was the most junior senior senator.
Sometimes a senator is sworn in during the middle of the two-year Congress. This did not occur in this Congress.
Order of service is based on the commencement of the senator's first term. Behind this is former service as a senator (only giving the senator seniority within their new incoming class), service as vice president, a House member, a cabinet secretary, or a governor of a state. The final factor is the population of the senator's state.
The most senior senators by class were Orrin Hatch (R-Utah) from Class 1, Thad Cochran (R-Mississippi) from Class 2, and Patrick Leahy (D-Vermont) from Class 3.