A transnational political party is a single political party with members or representatives in more than one country.
A well-known example is the Arab Baath Socialist Party, established as an Arab nationalist and socialist party aspiring to pan-Arab political union. The party's central governing body, the National Command, included representatives from its organisations in all the Arab countries where Baathists had a significant presence. Each branch of the party, in turn, had a local governing body, the Regional Command, and although practical power became centred in the Syrian and Iraqi Regional Commands and the National Command of each faction assumed an essentially symbolic role, the party split in 1966, with different factions taking control in Syria and Iraq, each faction retained a pan-Arab structure.
Another example of a transnational political party is Sinn Féin, which has 5 Members of Parliament in the United Kingdom Parliament, and 23 Teachtaí Dála in the Irish Dáil Éireann.
Some transnational organisations also have a party-political dimension. The best example of this is the European Union, in which groups of national political parties operate together when participating in EU institutions, especially the European Parliament, as European political parties, or "Europarties". However, Europarties are distinct from transnational political parties in that they do not operate at the national level.