Mucilage is a thick gluey substance, often produced by plants. Mucilage is another term for so called exopolysaccharides. These are sugar substances that cover the outside of, for example, unicellular or filamentous green algae and cyanobacteria. Amongst the green algae especially the group Volvocales are known to produce Exopolysaccharides at least in a certain part of their lifecycle.

Exopolysaccharides are the most stabilising factor for microaggregates and are widely distributed in soils. Therefore exoplysaccharide-producing "soil algae " play a vital role in the ecology of the world's soils.

Mucilage is edible, but tastes rather bland.