This open access book explores the history, production, and certification of reference materials for essential parameters in oceanography and provides a comprehensive understanding of them to readers. Because inorganic macro-nutrients, salinity, dissolved oxygen, and carbonate system parameters, including dissolved inorganic carbon, total alkalinity, and pH, are essential parameters in oceanography, they can be used to define biogeographic provinces, monitor ocean health, and detect decadal-scale oceanic climate changes. Without reference materials for these parameters, it would be difficult to produce reliable data sets or long-term baseline studies that are required to verify global change and oceanic stability. The book includes chapters on developing new reference materials for density, dissolved oxygen, dissolved organic carbon, dissolved organic matter, and trace metals, which are also important in oceanographic studies. The lead authors of each chapter regarding these parameters are top scientists in these areas; hence, this is the most comprehensive book of chemical reference materials for ocean science, written by experts in each field. The book is a useful resource for readers to find the latest information and status of certified reference materials (CRM) and reference materials (RM) and of ways to use CRM in their studies. We are in the middle of the United Nations Decade of Ocean Science for Sustainable Development (2021–2030), to which this book makes a timely contribution.