2018 United States elections

Elections were held in the United States on November 6, 2018. These midterm elections occurred during incumbent Republican president Donald Trump's first term. Although the Republican Party increased its majority in the Senate, Democratic incumbents and challengers vastly outperformed Trump's margin in Republican-leaning states, and unified Republican control of Congress and the White House was brought to an end when the Democratic Party won control of the House of Representatives. In what was widely characterized as a "blue wave" election, Democrats also gained governorships, other statewide offices, and state legislative chambers.

Democrats made a net gain of 40 seats in the United States House of Representatives, gaining a majority in the chamber and thereby ending the federal trifecta that the Republican Party had established in the 2016 elections. The Republican Party retained control of the United States Senate, making a net gain of two seats and defeating four Democratic incumbents in states that had voted for Trump in 2016. As a result of the 2018 elections, the 116th United States Congress became the first Congress since the 99th United States Congress (elected in 1984) in which the Democrats controlled the U.S. House of Representatives and the Republicans controlled the U.S. Senate. In state-level elections, Democrats picked up a net of seven governorships and several state legislative seats.

This was the first time since 1970 that one party gained Senate seats while losing House seats, which had also occurred in 1914 and 1962, and would go on to also happen in 2020, 2022, and 2024 as well. In the state elections, Democrats gained seven state governorships, control of approximately 350 state legislative seats, and control of six state legislative chambers.