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 XYZ Affair was a political and diplomatic episode in 1797 and 1798, early in the presidency of John Adams, involving a confrontation between the United States and Republican France that led to the Quasi-War. The name derives from the substitution of the letters X, Y, and Z for the names of French diplomats Jean-Conrad Hottinguer (X), Pierre Bellamy (Y), and Lucien Hauteval (Z) in documents released by the Adams administration.