2010 United States Senate elections

The 2010 United States Senate elections were held on November 2, 2010, from among the United States Senate's 100 seats. A special election was held on January 19, 2010, for a midterm vacancy in Massachusetts. 34 of the November elections were for 6-year terms to the Senate's Class 3, while other 3 were special elections to finish incomplete terms. Those 37 November elections featured 19 incumbent Democrats (7 of whom retired or were defeated in the primary) and 18 incumbent Republicans (8 of whom retired or were defeated in the primary).

After the 2008 elections, the Senate was composed of 58 Democrats, 40 Republicans, and 2 independents who caucused with the Democrats. However, in a January 2010 special election, Republicans picked up a seat in Massachusetts thereby reducing Democrats' majority to 57 seats.

Republicans won 4 seats held by retiring Democrats and also defeated 2 incumbent Democrats, for a Republican net gain of 6 seats. This was the first time since 1994 that Republicans successfully defended all of their own seats. This was also the fourth consecutive election of Class 3 senators where Democrats failed to gain seats. Despite the Republican gains, the Democrats retained a majority of the Senate with 51 seats plus the 2 Independents who caucused with them, compared to the 47 Republican seats. As of 2025, this was the last time Republicans won U.S. Senate seats in Illinois and New Hampshire.