This chapter examines developments in international law related to territorial sea, exclusive economic zones (EEZs), and continental shelves. After reviewing classifications of territorial sea and high seas, the chapter traces the emergence of a 200 nautical mile fishery zone, which led to a general embrace of EEZs by the United Nations Convention on the Law of the Sea in 1982. After initially opposing a 200 nautical mile EEZ, Japan adopted the straight baseline method of its territorial sea and fully established an EEZ in the late 1990s. The chapter also touches on issues related to EEZs, continental shelves, and fishery zones arising with Japan’s neighbors.