The Tethys Research Institute is a non-profit international research organisation supporting marine conservation through science and public awareness, founded in 1986 and headquartered at the Civic Aquarium of Milano, Italy. Tethys’ main goal is the conservation of the marine environment, achieved through the provision of scientific knowledge to conservation policy, the participation in the international conservation process, and public awareness. Over three decades of work, Tethys has generated one of the largest datasets on Mediterranean cetaceans, and communicated the results of its research in hundreds of scientific publications. In 1991 Tethys was the first to conceive and propose the creation of an iconic protected area, the Pelagos Sanctuary for Mediterranean Marine Mammals, the world’s first to be established beyond national jurisdiction. Since 1987 Tethys has involved, as research volunteers, thousands of citizens from all over the world in its conservation activities. Funding to Tethys derives from government and EC grants, private donors, and contributions from research volunteers. The work of Tethys is based on the collaboration of approximately 30 associates and assistants. See their work at https://www.tethys.org/.