Humboldt and the Ocean. A Synopsis of his Contributions to Marine Sciences. During his “Journey to the Equinoctial Regions of the New Continent” about 200 years ago, Alexander von Humboldt (1769–1859) made many oceanographic observations in the North Atlantic and Eastern Pacific Ocean. His main interest was the interrelation between climate and global ocean circulation, which is still one of the major topics in current marine research. Ever since, in 1790, he first saw the open ocean at the North Sea coast, when he, in the company of Georg Forster embarked on his trip to England, Humboldt had a longing for the ocean, especially the Pacific, and a strong interest in matters relating to oceanography. Unfortunately his marine texts are scattered over his major publications, many notes have never been published. Humboldt did not finish his decade-long work on “Oceanica,” a synopsis of his marine natural history ideas. Meanwhile it is generally accepted that Humboldt, although not an oceanographer in the modern meaning of the word, certainly belongs to the list of pioneers of marine sciences. Geographers and oceanographers of Kiel University, have especially covered Humboldts lasting marine legacy in the last century. His innovative and classical concepts of climate-driven thermohaline ocean circulation are background for some current international marine research projects.