The Leibniz Institute for Baltic Sea Research (, abbreviated IOW) is a research institution located in Warnemünde (Rostock), Germany. Its main focus lies in the interdisciplinary study of coastal oceans and marginal seas, especially related to oceanography of the Baltic Sea. It was founded in 1992 and is part of the Leibniz Association. The institute is the successor of the former Institute of Oceanography ("Institut für Meereskunde") which was part of the East German Academy of Science.
The institute is divided in four departments: physical oceanography, marine chemistry, biological oceanography, and marine geology. Central task of the institute is fundamental research but also teaching at the universities of Rostock and Greifswald. It employs about 160 people, and often cooperates with the University of Rostock. IOW has direct access to the research vessel Maria S. Merian and can access by request a variety of other medium-sized vessels from the German research fleet for longer trips and interdisciplinary tasks. The institute's facilities are financed by the German Federal Ministry of Education and Research and the Ministry of Education of Mecklenburg-Western Pomerania.
In addition to research and teaching, the IOW fulfills numerous tasks related to the transfer of scientific data. Its most important task is the transfer of knowledge to authorities and institutions active in environmental policy, such as the Federal Maritime and Hydrographic Agency (BSH) and the Federal Agency for Nature Conservation (BfN). The institute monitors and evaluates the condition of the Baltic Sea, which can directly feed into national and supranational environmental protection measures. The IOW is committed to transferring knowledge to the public. For example, the Warnemünde Evenings take place every summer; every two years the IOW participates in Baltic Sea Day and cooperates with schools and the media. The IOW collaborates with companies to improve the technologies used and develop new technologies.