The law of the sea is one of the oldest and, at the same time, most dynamic branches of international law. As such, it has been codified in a number of legally binding instruments, among which a predominant role is to be recognized to the United Nations Convention on the Law of the Sea (Montego Bay, 1982; UNCLOS), a complex and broad-ranging formulation of rules that seeks to regulate the use of the world’s oceans. Numerous scientific and technical considerations impinge upon the application of UNCLOS, just as UNCLOS has implications for the practice of marine science and technology. A profound interplay thus exists between the law of the sea and the disciplines of geodesy, hydrography, and geoscience, and the satisfactory realization of related technical issues is key to the orderly practice of international law in the ocean environment. The course contains a general overview of the law of the sea and the technical and scientific activities that are conducted in the world’s oceans, with particular regard to the identification of the relevant baselines and the construction of marine spaces subject to the sovereignty or jurisdiction of coastal States, as well as the law of maritime delimitations.