Krill oil is oil from a tiny, shrimp-like animal. Baleen whales, mantas, and whale sharks eat primarily krill. In Norwegian, the word "krill" means "whale food." People extract the oil from krill, place it in capsules, and use it for medicine. Some brand name krill oil products indicate that they use Antarctic krill.
Krill oil is an extract prepared from a species of Antarctic krill, Euphausia superba. Two of the most important components in krill oil are omega-3 fatty acids similar to those in fish oil, and phospholipid-derived fatty acids, mainly phosphatidylcholine.