Eisenia fetida, known under various common names, including redworms, brandling worms, "tiger worms" and red wiggler worms, is a species of earthworm adapted to the environment of decaying organic material. It thrives in rotting vegetation, compost, and manure. It is rarely found in soil, and instead, like Lumbricus Rubellus, prefers conditions where other worms cannot survive. Its specific name arises because, when roughly handled, it exudes a pungent liquid. This is presumably a chemical defense mechanism, although there appear to be no direct studies that have confirmed it confers protection against predators. It is closely related to the sibling species Eisenia andrei, also referred to as E. fetida andrei. The only simple way of distinguishing them is that E. fetida is lighter in color. Molecular analyses have confirmed their identity as separate species, and breeding experiments have also shown that they do not produce hybrids.

They are readily commercially available - primarily they are sold for vermiculture, owing to its remarkable ability to process organic matter into compost, but are also sold as bait. This process is known as vermiculture, with an end result of vermicompost.