The aim of this subject is to provide students with an in-depth introduction to the complex historical and conceptual reality that explains and justifies the central role played by Constitutions in the legal systems of present day democratic societies. Therefore, beginning with their remote medieval origins, the student will be introduced to the evolution of constitutional thought, through the gradual building and consolidation of the essential defining notions and principles of the new model of the State established as a result of the liberal revolutions, such as sovereignty, legality, separation of powers, or recognition and protection of individual and collective rights. But he or she will also have to opportunity to analyze and compare the different realization and formulation adopted by them through the most important historical constitutional texts, This will allow the student to become aware of the direct link existing between the solutions contained in each Constitution, including the current Spanish Constitution, and the particular political, economic and social circumstances at the moment of their writing.