Mare Liberum (English: The Free Sea 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. In The Free Sea, Grotius formulated the new principle that the sea was international territory and all nations were free to use it for seafaring trade. The disputation was directed towards the Portuguese Mare clausum policy and their claim of monopoly on the East Indian Trade.