The omega-3 polyunsaturated fatty acids (PUFA) such as eicosapentaenoic (EPA) and docosahexaenoic (DHA), have been recognized for their important role in health. EPA has several beneficial effects regarding coronary heart disease, while DHA has been found to be important for the development of the brain and retina. The increase in the consumption of fish oil, a commercial source of PUFA, has made necessary the search for new fish species rich in PUFA that could be used as raw material for the fish oil production. The lipid, fatty acid composition and natural antioxidant contents (carotene, tocopherol) were analyzed for the liver oil of Dasyatis brevis (arenera) and Gymnura marmorata (mariposa), two ray species commercially captured in the Gulf of California. The liver oil yield 25-50% (w/w) for D. brevis and 38-56% for G. marmorata. The triglyceride fraction was the major lipid class (577-758 mg/g) for both species, with smaller proportions of sterol esters, free sterols, polar lipids and diacyl glyceryl ethers. D. brevis showed a greater carotene and tocopherols concentration (6.9 mg/100 g, 25.3 mg/100 g, respectively) than G. marmorata (1.8 mg/100 g, 2.8 mg/100 g, respectively). The content of saturated and monoenoic fatty acid was similar for both species, however, the liver oil of G. marmorata had twice as much DHA than D. brevis. The composite percentage composition of DHA plus EPA with respect to the total of fatty acids in liver oil was 18% for G. marmorata and 16% for D. bzrevis. The liver oil of G. marmorata and D. brevis represent a new source of omega-3 PUFA that can be used for human and animal nutrition.