Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on selenite triglycerides as a novel food (NF) pursuant to Regulation (EU) 2015/2283, their safety when added for nutritional purposes to food supplements as a source of selenium and the bioavailability of selenium from this source, in the context of Directive 2002/46/EC. The proposed NF is the first lipophilic organic form of selenium so far described in the literature. It is composed by a mixture of individual Se-containing lipids which do not occur in nature. The Panel considers that the information provided on the composition of the NF does not allow a complete characterisation of the product. From the data provided to characterise the absorption, distribution, metabolism and excretion of the NF, it cannot be established in which chemical form Se is systemically available and if it can enter the functional Se body pool to fulfil Se physiological functions. The Panel considers that, since it is not demonstrated that the NF is converted to a known form of Se following ingestion and absorption, the NF is to be treated as a xenobiotic with unknown properties in the body. From a subchronic toxicity study in rats, the Panel derives a lowest observed adverse effect level (LOAEL) for general toxicity of 2 mg Se/kg body weight (bw) per day based on findings indicating liver as a target organ, as it has been shown for other studies on dietary Se. The Panel concludes that the NF is absorbed and provides Se, but in an unknown form of which the bioavailability has not been determined. The Panel also concludes that the safety of the NF under the intended conditions of use cannot be established