This article describes morphological characteristics and occurrence of Demodex lutrae n. sp., which was found on European otter Lutra lutra (Linnaeus, 1758) in Poland. The new species was found in hairy regions of otter skin, mainly in the head area. With respect to morphological features, D. lutrae is most similar to D. canis (Leydig, 1859) from the domestic dog Canis familiaris Linnaeus, 1758. The new species is a medium-sized demodecid mite (adult stages average 200 μm in length); characteristic features of these mites are hammer-shaped supracoxal spines (setae elc.p) on dorsal side of gnathosoma and palps with 3 conical spines. Demodex lutrae is the first representative of the family Demodecidae described in a host from the subfamily Lutrinae. This paper also contains a checklist of demodecid mites known from carnivores.