A running mate is a person running together with another person on a joint ticket during an election. The term is most often used in reference to the person in the subordinate position (such as the vice presidential candidate running with a presidential candidate) but can also properly be used when referring to both candidates, such as by saying Joe Biden and Kamala Harris, and Uhuru Kenyatta and William Ruto, were running mates in relation to the presidential elections held in the United States in 2020 and Kenya in 2013 respectively.

Running mates may be chosen, by custom or by law, to balance the ticket geographically, ideologically, or personally; examples of such a custom for each of the criteria are, geographically, in Nigerian general elections, in which a presidential candidate from the predominantly Christian south is typically matched with a vice presidential candidate from the predominantly Muslim north, and vice versa, ideologically, the Brazilian general elections in 2010 and 2014, where Dilma Rousseff of the left-wing Workers' Party ran alongside Michel Temer of the center-right Brazilian Democratic Movement Party, and, personally, the 2016 Bulgarian presidential election, in which both candidates who went on to the second round of voting, Rumen Radev and Tsetska Tsacheva, had running mates of the opposite gender. The objective is to create a more widespread appeal for the ticket and the results can range from assisting the resulting pair of candidates in appealing to a larger base of people to deterring voters who were initially inclined to vote for the running candidate, but may have been put off by the choice of the running mate.

The term is usually used in countries in which the offices of President and Vice President are both directly elected on the same ticket, in reference to a prospective Vice President. However, there are countries, such as the Philippines and (nominally) Cyprus, in which the President and Vice-President are elected on separate tickets, and frequently, this results in them being from different political parties - indeed, when the Philippine Vice-Presidential position was restored in 1987, only twice were the President and Vice-President elected from the same ticket, in 2004 and 2022. Further, in other countries, such as Botswana and Venezuela, the Vice-President is legally appointed by the President in all cases (unlike, for instance, the United States, in which the President appoints a Vice-President only in case of a vacancy, or Taiwan, in which the President nominates candidates for Vice-President in case of a vacancy and the Legislative Council elects one of them to fill the vacancy).

In cases of both separate elections and appointments, the President and Vice-President are not considered running mates because they are not elected on the same ticket.