Eisenia fetida (older spelling: foetida), known under various common names such as redworm, brandling worm, panfish worm, trout worm, tiger worm, red wiggler worm, red Californian earthworm (erroneously), etc., is a species of earthworm adapted to decaying organic material. These worms thrive in rotting vegetation, compost, and manure. They are epigean, rarely found in soil. In this trait, they resemble Lumbricus rubellus.
They have groups of bristles (called setae) on each segment that move in and out to grip nearby surfaces as the worms stretch and contract their muscles to push themselves forward or backward.
E. fetida worms are used for vermicomposting of both domestic and industrial organic waste. They are native to Europe, but have been introduced (both intentionally and unintentionally) to every other continent except Antarctica. Tiger worms are also being tested for use in a flushless toilet, currently being trialled in India, Uganda and Myanmar.
E. fetida is closely related to E. andrei, also referred to as E. f. andrei. The only simple way of distinguishing the two species is that E. fetida is sometimes lighter in colour. Molecular analyses have confirmed their identity as separate species, and breeding experiments have shown that they do produce hybrids. 
As with other earthworm species, E. fetida is hermaphroditic. However, two worms are still required for reproduction. The two worms join clitella, the large, lighter-colored bands which contain the worms' reproductive organs, and which are only prominent during the reproduction process. The two worms exchange sperm. Both worms then secrete cocoons which contain several eggs each. These cocoons are lemon-shaped and are pale yellow at first, becoming more brownish as the worms inside become mature. These cocoons are clearly visible to the naked eye.
- "Eisenia foetida". Fauna Europaea. 2004.
- Albanell, E.; Plaixats, J.; Cabrero, T. (1988). "Chemical changes during vermicomposting (Eisenia fetida) of sheep manure mixed with cotton industrial wastes". Biology and Fertility of Soils. 6 (3). doi:10.1007/BF00260823. ISSN 0178-2762.
- Orozco, F. H.; Cegarra, J.; Trujillo, L. M.; Roig, A. (1996). "Vermicomposting of coffee pulp using the earthworm Eisenia fetida: Effects on C and N contents and the availability of nutrients". Biology and Fertility of Soils. 22 (1–2): 162–166. doi:10.1007/BF00384449. ISSN 0178-2762.
- Maboeta, M.S.; Rensburg, L.van (2003). "Vermicomposting of industrially produced woodchips and sewage sludge utilizing Eisenia fetida". Ecotoxicology and Environmental Safety. 56 (2): 265–270. doi:10.1016/S0147-6513(02)00101-X. ISSN 0147-6513.
- "Testing the "Tiger Toilet"". US AID. May 26, 2016.
- "Friday Fellow: Tiger Worm" at Earthling Nature.