This is a complete list of United States senators during the 10th United States Congress listed by seniority from March 4, 1807, to March 3, 1809.
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 two main parties at this point were the Federalists (F), and Democratic Republicans (DR)