The 2010 United States elections were held on Tuesday, November 2, 2010, in the middle of Democratic President Barack Obama's first term. Republicans ended unified Democratic control of Congress and the presidency by winning a majority in the House of Representatives and gained seats in the Senate despite Democrats holding Senate control.

Republicans gained seven seats in the Senate (including a special election held in January 2010) but failed to gain a majority in the chamber. In the House of Representatives, Republicans won a net gain of 63 seats, the largest shift in seats since the 1948 elections. In state elections, Republicans won a net gain of six gubernatorial seats and flipped control of twenty state legislative chambers, giving them a substantial advantage in the redistricting that occurred following the 2010 United States census. The election was widely characterized as a "Republican wave" election.

The heavy Democratic losses in 2010 were mainly attributed to the passing of the Affordable Care Act along with a poor economic recovery from the Great Recession and large budget deficits. This marked the first election since 1858 that yielded a Republican-controlled House and a Democratic-controlled Senate. This configuration was also in place for most of the 107th Congress, but on account of Senator Jim Jeffords' party switch rather than the election results.

Candidates and voters in 2010 focused on national economic conditions and the economic policies of the Obama administration and congressional Democrats. Attention was paid to public anger over the Wall Street bailout signed into law by President George W. Bush in late 2008. Voters were also motivated for and against the sweeping reforms of the health care system enacted by Democrats in 2010, as well as concerns over tax rates and record deficits.^[2] At the time of the election, unemployment was over 9%, and had not declined significantly since Barack Obama had become President. Further eroding public trust in Congress were a series of scandals that saw Democratic Representatives Charlie Rangel and Maxine Waters, as well as Republican Senator John Ensign, all accused of unethical and/or illegal conduct in the months leading up to the 2010 election.

The fiscally-focused and quasi-libertarian Tea Party movement was a vocal force in mobilizing voters for Republican candidates nationwide. Their widespread exposure in the media contributed to the election's focus on economic, rather than social, issues. In the opinion of Fox News political analyst Dick Morris, a "fundamental change" occurred in which social issues did not dominate Republican activism in 2010, because "economic and fiscal issues prevail. The Tea Party has made the Republican Party safe for libertarians."^[3]

Immigration reform had become an important issue in 2010, particularly following the passage of Arizona Senate Bill 1070, officially known as the Support Our Law Enforcement and Safe Neighborhoods Act. The Act greatly enhanced the power of Arizona's law enforcement agencies to investigate the immigration status of suspected illegal immigrants and to enforce state and national immigration laws. The Act also required immigrants to carry their immigration documentation on their person at all times. Its passage by a Republican-led legislature and its subsequent and very public signing by Jan Brewer, the Republican Governor of Arizona, ignited protests across the Southwest and galvanized political opinion among both pro-immigration Latino groups and Tea Party activists, many of whom supported stronger measures to stem illegal immigration.

The passage of the controversial Patient Protection and Affordable Care Act also contributed to the low approval ratings of Congress, particularly Democrats, in the months leading up to the election. Many Republicans ran on a promise to repeal the law, and beat incumbent Democratic opponents who had voted in favor of the Patient Protection and Affordable Care Act.

On November 2, 2010, various cities, counties, school boards, and special districts (in the United States) witnessed elections. Some elections were high-profile.

• Luzerne County, Pennsylvania: The voters of Luzerne County adopted a home rule charter by a margin of 51,413 to 41,639.^[12][13] This changed the county’s government from a board of county commissioners to a council-manager form of government. The following year (in 2011), the first general election for the new assembly was held. The first council members were sworn in on January 2, 2012.^[14]

High-profile mayoral elections are listed below:

• Honolulu, Hawaii: Incumbent mayor Mufi Hannemann resigned on July 20, 2010, to run for Governor of Hawaii. The city's Managing Director Kirk Caldwell served as acting mayor until Peter Carlisle was elected in a special election on September 18.
• Louisville, Kentucky: Incumbent mayor Jerry Abramson declined to run for a third consecutive term in order to run for Lieutenant Governor of Kentucky in 2011. Greg Fischer was elected as the successor.
• New Orleans, Louisiana: Incumbent mayor Ray Nagin was term-limited out of office. Mitch Landrieu was elected as the new mayor on February 6.
• Washington, D.C: Incumbent mayor Adrian Fenty was defeated in the Democratic primary by Vincent C. Gray, who then went on to win the general election.

Approximately 82.5 million people voted.^[15] Turnout increased relative to the last U.S. midterm elections without any significant shift in voters' political identification.^[16]

Bold indicates a change in control. Note that not all states held gubernatorial, state legislative, and United States Senate elections in 2010.