The 1966 United States House of Representatives elections was an election for the United States House of Representatives on November 8, 1966, to elect members to serve in the 90th United States Congress. They occurred in the middle of President Lyndon B. Johnson's second term. As the Vietnam War continued to escalate and race riots exploded in cities across the country, Johnson's popularity had fallen, and the opposition Republican Party was able to gain a net of 47 seats from Johnson's Democratic Party, which nonetheless maintained a clear majority in the House. This was also the first election that occurred after the Voting Rights Act of 1965 became law, the first time since 1870 that a Republican won a House seat in Arkansas, and the first since 1876 that the party did so in South Carolina.

The 1964 United States House of Representatives elections was an election for the United States House of Representatives on November 3, 1964, to elect members to serve in the 89th United States Congress. They coincided with the election to a full term of President Lyndon B. Johnson. Johnson's landslide victory over Barry Goldwater allowed his Democratic Party to gain a net of 36 seats from the Republican Party, giving them a two-thirds majority in the House. The election also marked the first time since Reconstruction that Republicans made inroads in the Deep South, with Republicans winning seats in Georgia for the first time since 1874, and Alabama and Mississippi since 1876.