The 2012 United States presidential election in Missouri took place on November 6, 2012, as part of the 2012 United States presidential election, in which all 50 states plus the District of Columbia participated. Missouri voters chose 10 electors to represent them in the Electoral College via a popular vote pitting incumbent Democratic President Barack Obama and his running mate, Vice President Joe Biden, against Republican challenger and former Massachusetts Governor Mitt Romney and his running mate, Congressman Paul Ryan.

Missouri was won by Romney, who took 53.64% of the vote to Obama's 44.28%, a margin of 9.36%. Although it was a battleground in past elections, and considered a bellwether up until 2008, Missouri trended in the early 21st century toward the Republicans, having been the only long-time swing state to be won (albeit narrowly) by Republican John McCain in 2008. Consequently, the state was not heavily contested by either side in 2012, and Romney ultimately carried Missouri by the largest margin since Ronald Reagan's 1984 landslide.

Romney became the second Republican to carry Missouri and lose the presidency just four years after John McCain's narrow victory in the state, with Obama also becoming the only Democrat to ever win two terms in the White House without carrying the state at least once. Despite losing the state, Obama remains the last Democratic nominee to lose Missouri by less than 10%, as of 2024.

The 2012 Missouri Republican presidential primary took place on February 7 and the caucuses ran from March 15 to March 24, 2012, except for one rescheduled for April 10. The primary election did not determine which delegates would be sent to the national convention; this is instead determined indirectly by the caucuses and directly by the Missouri Republican congressional-district conventions on April 21 and the state convention on June 2.

The unusual situation of having both the primary election and the caucus for the same party in the same election year in Missouri arose as a result of a change in the nominating rules of the Republican Party. State primaries in Missouri were previously held in early February. In September 2008, the Republican National Committee adopted a set of rules which included a provision that no states except Iowa, New Hampshire, South Carolina, and Nevada were allowed to begin the process of delegate selection (including binding primary elections) before the first Tuesday in March of an election year. In 2011, the Republican-controlled Missouri General Assembly attempted to move the primary election to mid-March, but the bill was vetoed by Democratic Governor Jay Nixon because of a provision limiting his power to fill vacancies in statewide elected offices. In a compromise solution, it was decided that Republican primary election would be made non-binding and instead delegates would be nominated by separate caucuses in late March, a move estimated to cost the state US$7,000,000.

This marks the first time since 1996 that Missouri Republicans used a caucus system to nominate delegates to the Republican National Convention.

The primary was not to affect the selection of Missouri's delegates to the 2012 Republican National Convention, so it had no official effect on the nomination and was widely described beforehand as a "beauty contest". However it was seen as an opportunity for Rick Santorum to face off against Mitt Romney due to the absence of Newt Gingrich, who missed the filing deadline and was not on the ballot. Santorum was the only candidate to actively campaign in the state ahead of the primary.

The primary election was won by Santorum, who also won the Colorado and Minnesota Republican caucuses held that day.