This article addresses the heritage of Grotius's concept of common goods (res communes) as developed in his seminal work Mare liberum. This contribution identifies the basic tenets of Grotius's thinking on the nature of common property and identifies the relevance of these ideas for the present day management of global commons, i.e., the areas and natural resources beyond the limits of national jurisdiction. Successively, the article examines the regimes for: the deep seabed, the high seas, and marine mammals; outer space, particularly the moon; the two polar regions; and the atmosphere, in particular the ozone layer and the climate system. The article demonstrates how some of the original tenets of Grotius's concept of res communis – in particular the idea of inexhaustibility – can no longer be upheld and how the freedom of access to the global commons has become increasingly qualified and supplemented, if not replaced by a new law of international co-operation aimed at conservation and sustainable use of natural wealth and resources beyond the limits of national jurisdiction. The global commons function as laboratories for the testing of new principles of international law and new forms of international co-operation, which can be said to clearly build upon the Grotian heritage.