Spanish Abstract: El enriquecimiento sin causa es una figura juridica clasica surgida en el Derecho Civil. Sin embargo, en las ultimas decadas, su mayor desarrollo se ha dado en la jurisprudencia contencioso administrativa, en donde la figura se ha adoptado para proteger a particulares que se han empobrecido de forma injustificada y a favor del Estado, quienes se encontraban desprovistos de proteccion juridica. Asi, el Consejo de Estado adopto la estructura basica del enriquecimiento sin causa, pero le anadio algunos cambios. En este orden, este articulo pretende, a traves del Analisis Economico del Derecho, contrastar estas dos interpretaciones y, a partir de un juicio de eficiencia, determinar cual es la mas adecuada para el mundo juridico y economico. English Abstract: The unjust enrichment is a classical legal figure emerged in Civil Law. However, in the last decades, its greatest development has been given in administrative jurisprudence, where the figure has been adopted to protect individuals who have become impoverished in a unjustified and in favor of the State, who were deprived of legal protection. Thus, the Council of State adopted the basic structure of the unjust enrichment, but added some changes. In this order, this article intends, through the Economic Analysis of Law, to contrast these two interpretations and, based on an efficiency judgment, determine which is the most suitable for the legal and economic world.