This paper deals with the concept of simulated contract in the light of its theory and doctrinal development, investigating its historical origin, the forms it adopts and the legal consequences in private law, its most relevant classifications, or types, as well as the various schools that have developed the effects of this business phenomenon. I conclude with some reflections about the limits of the faculty of simulating contracts.La presente contribución revisa los aspectos fundamentales de la simulación de contrato, su declaración judicial y la relación con otras conductas afines, desarrollados por la doctrina del derecho privado español. Su relevancia radica en que se trata de un fenómeno expansivo y vigente, cuyo estudio y desarrollo se encuentra inacabado.