The objectives of this technical paper are to provide measures of the status and potential for offshore mariculture development from a spatial perspective, which are comprehensive of all maritime nations and comparable among them; to identify nations not yet practicing mariculture that have a high offshore potential for it; and to stimulate interest in detailed assessments of offshore mariculture potential at national levels. Mariculture accounts for about one-half of total aquaculture production. Nearly all of mariculture is inshore, but there is an impetus for mariculture to move to the unprotected waters of the open sea. Issues at the local level include competition for space, water quality problems, and a negative public perception of mariculture’s environmental and aesthetic impacts. At the global level, there is concern for food security with expanding populations along with the conviction that the potential of the world’s oceans to supplement the food supply is vastly underutilized. Prospecting for suitable locations is a critical part of spatial planning for offshore mariculture’s near-future development.