"Contractualism" refers to the diverse theories that maintain that the obligatory nature of norms rests on the consent of those bound by them. However, this general characterization overlooks crucial differences among the different contractualist theories. The article analyzes diverse typologies in order to highlight these differences and reach a more precise characterization of contractualism. It concludes that the distinction between hypothetical and ideal consent made by some of these versions makes it impossible to formulate a univocal definition of contractualism.