Metal catalysis has driven innovation in organic synthesis during the last half-century. An alternative to the traditional strategy of developing catalysts with a single metal center is the combined use of more than one metal complex and the design of their cooperative action to achieve new synthetic transformations. With the rich chemistry of metal catalysis that has been developed over the last five decades, as well as recent advancements in organocatalysis and emerging photoredox catalysis, one can imagine that cooperativity of these known catalytic approaches could enable novel synthetic transformations that have been highly challenging via conventional single-site metal catalysis.