The Missouri Plan (originally the Missouri Nonpartisan Court Plan, also known as the merit plan, or some variation) is a method for the selection of judges. It originated in Missouri in 1940 and has been adopted by many states of the United States. Similar methods are used in some other countries.

Under the Plan, a non-partisan commission reviews candidates for a judicial vacancy. The commission then sends to the governor a list of candidates considered best qualified. The governor then has sixty days to select a candidate from the list. If the governor does not make a selection within sixty days, the commission makes the selection.

At the next general election after the completion of one year's service, the judge must stand in a retention election. If a majority votes against retention, the judge is removed from office, and the process starts anew. Otherwise, the judge serves out a full term.

As of 2016, 38 states have a form of merit-based selection and retention method for some or all judges. Twenty-five states have a nominating commission to screen all candidates of the state courts of last resort. Eight states have commissions which fill interim vacancies on the highest courts. Twenty states utilize retention elections for judges who wish to serve on highest state courts beyond their initial term.

Under the Missouri Nonpartisan Court Plan, a nonpartisan judicial commission reviews applications, interviews candidates and selects a judicial panel. For the Supreme Court and Court of Appeals, the Appellate Judicial Commission makes the selection. It is composed of three lawyers elected by members of the Missouri Bar (the organization of all lawyers licensed in this state), three citizens selected by the governor, and the chief justice, who serves as chair. Each of the three geographic districts of the Court of Appeals must be represented by one lawyer and one citizen member on the Appellate Judicial Commission.

Each of the circuit courts in Clay, Greene, Jackson, Platte, and St. Louis Counties, and the city of St. Louis has its own circuit judicial commission. These commissions are composed of the chief judge of the court of appeals district in which the circuit is located, plus two lawyers elected by the bar and two citizens selected by the governor. All of the lawyers and citizens must live within the circuit for which they serve the judicial commission.

In line with other reforms urged during the Progressive Era, legal scholars put forth ideas in the first decades of the 1900s to reduce or remove the role of politics in the selection of judges, particularly circuit judges with responsibilities over the day-to-day work of the courts. An example of this advocacy is the merit selection program urged by Albert M. Kales in his work Unpopular Government in the United States (1914).

Support for merit selection increased due to the perceived corruption of urban political bosses. Missouri voters adopted the system by initiative petition in November 1940 after several very contentious judicial elections, which were heavily influenced by the political machine of Tom Pendergast. Most associate and circuit judges are elected. However, the state constitution requires such judges in Jackson County (Kansas City) and the city of St. Louis to be selected under the nonpartisan system. Similarly, the voters in Clay and Platte counties (parts of Kansas City), St. Louis county, and Greene County (Springfield) have elected to appoint such judges under the nonpartisan system. After Missouri adopted this method for selecting judges, several other states adopted it, either in full or in part. The plan was put forth by a committee chaired by Luther Ely Smith, "founder" of the Gateway Arch National Park.