Bartolomé de las Casas was one of the main defenders of the rights of the Indians and, later, of African slaves. His contribution went beyond the religious and political sphere, where his proposals more properly belonged, to influence many other authors and the society of his time, as well as posterity. After describing the Dominican's contributions and life trajectory, this article attempts to relate both to the work and life of another giant of Spanish literature, Miguel de Cervantes. The second part of the article analyses the relationship between the lives of the two figures and the grounds for linking their works. The third part of the article analyses Cervantes' treatment of slavery and captivity, an issue that the author of Don Quixote himself suffered personally and of which he left abundant testimonies in his works.