During the last 40 years, members of the Operational Marine Sciences and Sustainability Unit have carried out studies in different areas of the oceans, particularly, the Mediterranean Sea. Phytoplankton samples were always taken with high-quality chlorophyll analyses as well as physical and chemical observations. Many of the phytoplankton data sets went unpublished. Zoila Velásquez included, in her Ph.D. thesis, an Inventory of Phytoplankton Taxa in the NW Mediterranean. In addition to her own observations, Dr. Velásquez consulted leading authors’ publications including those of phytoplankton taxonomy pioneers such as Gourret, Pavillard, etc. She also obtained unpublished phytoplankton lists from a number of colleagues (R. Margalef, M. Estrada, etc.) in the Institut de Ciències del Mar in Barcelona. The present compendium includes taxa cited in more than 35 publications.