Mare Liberum (or The Freedom of the Seas) is a book in Latin on international law written by the Dutch jurist and philosopher Hugo Grotius, first published in 1609.

Grotius wrote the treatise while being a counsel to the Dutch East India Company over the seizing of the Santa Catarina Portuguese carrack issue.

In chapter I, he laid out his objective, which was to demonstrate "briefly and clearly that the Dutch [...] have the right to sail to the East Indies", and, also, "to engage in trade with the people there".

[5] However, Hakluyt's translation was only published for the first time in 2004 under the title The Free Sea as part of Liberty Fund's "Natural Law and Enlightenment Classics" series.

The second translation was by Ralph Van Deman Magoffin, associate professor of Greek and Roman History at Johns Hopkins University.