Krill oil represents an interesting source of bioactive lipid components, being suitable as a functional ingredient. This oil is characterized by its high concentration of long-chain omega-3 fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The contents of EPA and DHA were similar to those in fish oils, but with the difference that almost the half are located in phospholipids (mainly phosphatidylcholine). This might explain its higher absorption and bioavailability. This highly unsaturated oil maintains stable due to the presence of astaxanthin, a potent antioxidant, which assures the stability of the omega-3 fatty acids. However, there is lack of investigations reporting a deep comprehensive description of the krill oil (KO) lipid composition. The characterization includes new data of its neutral and polar components and the identification of triacylglycerols, diacylglycerols, and molecular species that has been done by different chromatographic techniques as gas chromatography-mass spectrometry/flame ionization detector (GC-MS/FID), flash chromatography-evaporative light scattering detector (FC-ELSD), and HPLC-ELSD. Also phospholipid molecular species by using ultraperformance liquid chromatography/quadruple-time-of-flight mass spectrometry (UPLC/QToF-MS) have been determined.