The 5th United States Congress was a meeting of the legislative branch of the United States federal government, consisting of the United States Senate and the United States House of Representatives. It met at Congress Hall in Philadelphia, Pennsylvania, from March 4, 1797, to March 4, 1799, during the first two years of John Adams' presidency. In the context of the Quasi-War with France, the Alien and Sedition Acts were passed by Congress. The Acts were overwhelmingly supported by the Federalists and mostly opposed by the Democratic-Republicans. Some Democratic-Republicans, such as Timothy Bloodworth, said they would support formally going to war against France but they opposed the Alien and Sedition Acts which Bloodworth and others believed were unconstitutional.

The apportionment of seats in this House of Representatives was based on the 1790 United States census. Both chambers had a Federalist majority.

Details on changes are shown below in the "Changes in membership" section.

This list is arranged by chamber, then by state. Senators are listed in order of seniority, and representatives are listed by district.

Senators were elected by the state legislatures every two years, with one-third beginning new six-year terms with each Congress. Preceding the names in the list below are Senate class numbers, which indicate the cycle of their election. In this Congress, Class 1 meant their term began in this Congress, requiring reelection in 1802; Class 2 meant their term ended with this Congress, requiring reelection in 1798; and Class 3 meant their term began in the last Congress, requiring reelection in 1800.

The count below reflects changes from the beginning of this Congress

There were 9 resignations, 2 deaths, 1 expulsion, 1 late selection, and 2 elections to replace appointees. Neither party had a net gain of seats.

There were 9 resignations and 3 deaths. The Federalists had a 1-seat net loss and the Democratic-Republicans had a 1-seat net gain.