Detritus may refer to:

• In geology, detritus is the name for loose fragments of rock that have been worn away by erosion.
• In biology, detritus is organic waste material from decomposing dead plants or animals. This detritus is an important source of nutrients for so-called "detritus feeders" or detritovores. These form, in many ecosystems, the base of the food chain. What is left behind by the detrivores is then further broken down and recycled by decomposers, such as bacteria and fungi.
• Detritus is a character in the Discworld novels of Terry Pratchett