The 90th United States Congress was a meeting of the legislative branch of the United States federal government, composed of the United States Senate and the United States House of Representatives. It met in Washington, D.C., from January 3, 1967, to January 3, 1969, during the last two years of President Lyndon B. Johnson's second term in office.

The apportionment of seats in this House of Representatives was based on the 1960 United States census.

Both chambers had a Democratic majority - maintaining a supermajority in the Senate, but losing seats in the House, costing them supermajority status in that chamber. Along with President Johnson, the Democrats maintained an overall federal government trifecta.