The southern sea otter (Enhydra lutris nereis), also known as California sea otter, was listed as threatened in 1977 under the Endangered Species Act. Since 1985, stranded otters from throughout their California coastal range have been collected and analyzed to inform resource management on recovery and conservation of the species. This data set is a complete 34 year compilation. Future annual stranding recovery information will be published when available. Stranded sea otters were collected by members of the sea otter stranding network (USGS, California Department of Fish and Wildlife (CDFW), Monterey Bay Aquarium (MBA), and the Marine Mammal Center (TMMC)) during routine beach walks and (more often) following reports by the general public and representatives of management agencies (e.g., California State Parks, Municipal Harbor Patrols, County Parks). The intent is to document and recover all stranded southern sea otters; however, certain areas such as the Big Sur coastline are under-represented due to access and logistical constraints. All beach-cast sea otters (most of which are dead, but also live moribund animals that would have died without intervention) are examined and the date and geographic location of each recovered animal is recorded, as well as the sex, age class, general condition, and circumstantial cause(s) of death if evidence is apparent, e.g., boat-strike trauma, net entanglement, shark bite wounds.