Malacolimax tenellus (lemon slug) is a European species of air-breathing land slug, a terrestrial gastropod mollusc in the family Limacidae.
The body is yellow in color, from pale to bright yellow, sometimes with a hint of orange, and the sole is pale yellow, and produces yellow slime. The head is gray or lilac and the tentacles are typically tinged with purple or are a blue-grey. It can grow up to .
This species is European, with a range extending from the Pyrenees to European Russia and northwards into Scandinavia. But it is absent from Ireland and most of southern Europe.
This species lives in both deciduous and coniferous woodland. It typically feeds at night on fungi.
Parasites of Malacolimax tenellus include: