The paper presents a scientific and human profile of Antonio Marongiu, born in 1902 in Sardinia (Siniscola). He graduated first in Law and then in Political Sciences, at the University of Rome, becoming full professor since 1934. He also taught in Cagliari, Macerata and Pisa. The paper aims to introduce the fundamental and little-known contribution made by Marongiu to the foundation of History of Political Institutions, of which he held the first chair in Rome from the academic year 1967-68 and which he contributed to include in the Charters of the Faculties of Political Science. He is also known for settling the question of method still valid today and for his active involvement in the International Commission for the History of Representative and Parliamentary Institutions, which he acted as president from 1970 and the following 10 years.