San Jorge Gulf (SJG) is home to a complex ecosystem that provides a variety of high-quality services to the regional and national economy of Argentina, particularly oil and gas, fisheries, and tourism. The gulf is located in the central region of Patagonia between 45°S and 47°S, covers an area of 39,340 km2, and is open to the Atlantic Ocean. Until recently, although some interdisciplinary scientific information had been gathered for the SJG, very little had been published in widely accessible journals. This special issue of Oceanography aims to document fundamental research into SJG biological, physical, chemical, and sedimentary processes undertaken in the last few years. More than 40 researchers, students, and technicians from Québec (Canada) and Argentina participated in the initial efforts of PROMESse (Multidisciplinary program for the study of the ecosystem and geology of the San Jorge Gulf and the coastal region of the province of Chubut), which closely matches the Argentinean government’s Pampa Azul Initiative. The general objective of the PROMESse research program is to conduct an integrated study of the SJG, with the results serving as a baseline for the sustainable management of the ecosystem services of this rich marine ecosystem. This bilateral effort included two workshops, held in 2017, one in Rimouski (Québec, Canada) and another in Comodoro Rivadavia (Chubut, Argentina), that led to the 15 articles published in this special issue.