The expression ‘living resources’ occurs 47 times in the United Nations Convention on the Law of the Sea’s provisions, but it does not give a legal definition of the term. To clarify the meaning of this expression and its legal scope in the evolution of the law of the sea, it is mandatory to analyse its historical background, its appearance and meanings in different stages of this evolution: before the adoption of the UNCLOS, in the time of its negotiations, and after it enters into force with an emphasis on the integration of environmental principles in the law of the sea, and the ongoing work before the United Nations on an international legally binding instrument for the conservation and sustainable use of the biological diversity in areas beyond national jurisdiction. This study would aim to clarify the legal meaning of ‘marine living resources’ and how using a broader semantic field in different legal instruments or other areas of international law shaped the legal framework of the conservation and sustainable use of marine living resources.