Osteofluorosis is a condition of abnormal skeletal growth that occurs with chronic overexposure to fluoride (F-), generally in water or the diet. This condition has been described in terrestrial mammals for thousands of years but was only recently diagnosed in a marine mammal species, three unrelated California sea lions (CSLs, Zalophus californianus). This study developed bone F- reference intervals to assist with health monitoring efforts in CSLs and provide groundwork for future studies investigating exposure sources that can lead to osteofluorosis development in this species. Eighty-seven stranded CSLs were sampled opportunistically at necropsy under NOAA permit, and bone samples were analyzed on a dry weight basis using a F- ion-selective electrode method. The mean and (95%, 95%) upper tolerance intervals of bone F- concentrations were calculated for the species, both sexes, and all age classes, and a mean and standard deviation were provided for the different bone types. The CSL species mean and upper tolerance intervals were 1344 ppm (2831, 3276 ppm). The mean and upper tolerance intervals for the sexes were: female = 1329 ppm (2487, 2876 ppm); male = 1359 ppm (3255, 3958 ppm). A partial Pearson correlation demonstrated a strong correlation for all tested bones except for the mandibular canine tooth. The data also demonstrated a trend of increasing bone F- concentrations with age, though no difference was obvious between the sexes. Bone samples from 40 southern sea otters (SSOs, Enhydra lutris nereis) were also obtained and analyzed for F- content to regionally contrast with the CSL data. The SSOs bone F- concentrations were notably lower than the CSL data and varied somewhat in trends. Several CSL prey species were also analyzed, and many contained high F- concentrations, demonstrating a potential exposure pathway for CSLs and other predatory marine species.