The 1982 United Nations Convention on the Law of the Sea (UNCLOS) remains the cornerstone of global ocean governance. However, it lacks effective provisions or mechanisms to ensure that all ocean space and related problems are dealt with holistically. With seemingly no opportunity for revision due to the Conventions burdensome amendment provisions, complementary mechanisms dealing with such aspects of global ocean governance including maritime transport, fisheries, and marine environmental sustainability, have been developed under the aegis of the United Nations and other relevant international organizations. This approach is inherently fragmented and unable to achieve sustainable global ocean governance. In light of the Sustainable Development Goals (SDGs), particularly Goal 14, the IMLI Treatise proposes a new paradigm on the basis of integrated and cross-sectoral approach in order to realise a more effective and sustainable governance regime for the oceans. This volume focuses on the role of UN as the central intergovernmental organization responsible for global ocean governance. It examines the ocean governance challenges and how the present legal, policy, and institutional frameworks of the UN have addressed these challenges. It identifies the strengths and weaknesses of UN legal structures and offers tangible proposals to realize the ambition of a global ocean governance system.