The 1986 United States elections were held on November 4 and elected the members of the 100th United States Congress. The elections occurred in the middle of Republican President Ronald Reagan's second term. Democrats regained unified control of both chambers of Congress for the first time since the 1980 elections.

1986 United States elections

← 1984          1985          1986          1987          1988 → Midterm elections
Election day	November 4
Incumbent president	Ronald Reagan (Republican)
Next Congress	100th
Senate elections
Overall control	Democratic gain
Seats contested	35 of 100 seats (34 Class 3 seats + 1 special election)
Net seat change	Democratic +8
1986 Senate election results   Democratic gain   Democratic hold   Republican gain   Republican hold
House elections
Overall control	Democratic hold
Seats contested	All 435 voting seats
Popular vote margin	Democratic +9.9%
Net seat change	Democratic +5
1986 House of Representatives election results   Democratic gain   Democratic hold   Republican gain   Republican hold
Gubernatorial elections
Seats contested	38 (36 states, 2 territories)
Net seat change	Republican +8
1986 gubernatorial election results Territorial races not shown   Republican hold   Republican gain   Democratic hold   Democratic gain

In an instance of the six-year itch phenomenon, the Democrats won a net gain of eight seats to recapture control of the United States Senate, taking back the chamber for the first time since the 1980 elections. Democrats won the national popular vote for the House of Representatives by a margin of 7.7 percentage points, making a net gain of five seats.^[1] Despite Democratic congressional gains, in the gubernatorial elections, the Republican Party picked up a net of eight governorships, making 1986 the last midterm election until 2022 that the president's party made gubernatorial gains.

The national campaign centered largely around the Senate, where Republicans defended a large freshman class of Senators. Despite sweeping Democratic gains, many of the losing Republicans incumbents lost by small margins. The Republican loss of the Senate put an effective check on any further major conservative legislation during the Reagan administration. The elections also had a major impact on the Supreme Court, as Republican losses helped ensure that Robert Bork's nomination to the Supreme Court would be defeated by the Senate. After the Senate rejected the conservative Bork, Reagan instead nominated Anthony Kennedy, who became a critical swing vote on the court.^[2]