O Clássico is the name given in football to matches between Portuguese clubs S.L. Benfica and FC Porto. Originally, the term O Clássico only referred to games played in the league, but now tends to include matches that take place in other domestic competitions such as the Taça de Portugal, Taça da Liga and Supertaça Cândido de Oliveira. Despite being the two most decorated Portuguese clubs in European football, with seven European trophies between them, they have never faced each other in a European competition. Benfica and Porto are two of the three clubs known as the "Big Three" in Portugal, the other being Sporting CP.

Sport Lisboa e Benfica, commonly known as Benfica, is a professional football club based in Lisbon, Portugal, that competes in the Primeira Liga, the top flight of Portuguese football.