United Nations secretary-general selection is the process of selecting the next secretary-general of the United Nations. To be selected as secretary-general, a candidate must receive the votes of at least nine members of the United Nations Security Council, with no vetoes from permanent members. The secretary-general is then appointed by a majority vote of the United Nations General Assembly.

Although the process is informally called an election, the United Nations refers to it as the "procedure of selecting and appointing the next United Nations secretary-general." Since the General Assembly has never refused to appoint the person recommended by the Security Council, it can be said that the selection of the Security Council determines the next secretary-general of the United Nations.

Few formal rules govern the selection of the secretary-general of the United Nations. The only guiding text, Article 97 of the United Nations Charter, states "The Secretary-General shall be appointed by the General Assembly upon the recommendation of the Security Council." The charter's minimal language has since been supplemented by other procedural rules and accepted practices. In 1946, the General Assembly adopted a resolution stating it was "desirable for the Security Council to proffer one candidate only for the consideration of the General Assembly, and for debate on the nomination in the General Assembly to be avoided."

The selection is subject to the veto of any of the five permanent members of the Security Council. If a permanent member vetoes a candidate, it is not counted as a veto of a Security Council Resolution, as the votes are kept secret. To break the deadlocked selection of 1981, the Security Council began to take straw polls by secret ballot. The system of straw polls was set down on paper in 1996 as the Wisnumurti Guidelines.

Several months before the current secretary-general's term ends, a straw poll is taken by secret ballot among the members of the Security Council using a form of score voting. Votes are cast to "encourage" or "discourage" a particular candidate, or express "no opinion." The votes of the permanent members are mixed in with the votes of the rotating members. Based on the results of the straw poll, candidates may withdraw, and new candidates may be nominated.

The next round of straw polling reveals the existence of any vetoes. The permanent members vote on red paper, and the rotating members vote on white paper. If any permanent members vote "discourage," this is treated as a likely veto. Straw polling continues until a candidate has no vetoes and more "encourage" votes than the other candidates. The Security Council then votes to recommend the candidate to the General Assembly. Since 1996, the vote has been taken by acclamation so that the secretary-general is recommended unanimously.

In the last stage, the General Assembly formally appoints the recommended candidate as secretary-general. In every selection except 1950, the General Assembly has voted by acclamation so that the secretary-general is appointed unanimously. No candidate recommended by the Security Council has ever been rejected by the General Assembly. However, the threat of a negative vote in the General Assembly hangs over the deliberations of the Security Council.

The process of selecting a secretary-general is often compared to a papal conclave. The voting is restricted to a small group of countries, takes place in secret, goes through multiple rounds, and is easily deadlocked. Although the ballots are not burned to make black and white smoke, the ballot papers are printed on red and white paper. Although the voting is secret, diplomats always leak the results to journalists. Candidates for secretary-general can be vetoed by the permanent members, just as popes could be vetoed by Catholic Great Powers until the 1903 conclave.