The Institute of International Law is a scientific organisation. It was established in 1873 in Ghent on the initiative of the Belgian lawyer Gustave Rolin-Jaequemyns. The main task of the Institute is to study the applicable international law in order to monitor whether it evolves in line with the principles of justice and humanitarianism.

The Institute does not intervene directly in international conflicts. However, its resolutions, although not binding, influence the positions taken by governments and parliaments. The Institute holds biennial sessions (until 1957, some annual sessions had been held). Between the sessions, scientific commissions work on particular topics. Two sessions took place in Poland: one in Warsaw in 1965 and one in Cracow in 2005.

The Institute brings and implements specific proposals aimed at the gradual development of an international community which respects law and justice. Among other things, the Institute adopted resolutions relating to the establishment and functioning of the International Court of Justice.