The Eurasian otter, also known as the European otter, is a semi-aquatic mammal found in Europe, Asia, and parts of Africa. There are several synonyms for the Eurasian otter, including the common otter, European river otter, Old World otter, and Lutra lutra. In addition, there are many regional names for the species, such as the loir de riviere in France, the vidra in Romania, and the wonsdompig in Sweden. The Eurasian otter is an important species in many ecosystems, serving as an indicator of water quality and playing a key role in maintaining healthy aquatic environments.