In Western culture, oceans have traditionally been perceived as timeless, separate from society and practically boundless in resources and absorptive capacity. As a result, the entangled histories of people and marine environments have largely been neglected in historical research. This is changing with the development of marine environmental history together with increasing recognition of oceans’ vulnerability and importance in earth systems. Against this background, we review the current state of historical knowledge of how different actors within Swedish society have perceived and impacted the Baltic Sea environment, as well as discovered and responded to marine environmental change. We find that this environmental history, as distinct from other forms of historical research, has so far received limited attention. While the environmental histories of terrestrial resources in Sweden – including forests, agriculture, minerals and energy – have been thoroughly studied, there is little comparative knowledge about the formation and development of the major scientific institutions and public agencies involved in Baltic Sea governance. In light of this, we discuss how knowledge about Sweden’s marine environmental history can be improved, and the importance this may have for the future sustainability of the Baltic Sea.