For other uses, see Mold (disambiguation).

Molds (British English: moulds) are various fungi that cover surfaces as fluffy mycelium and usually produce masses of asexual, sometimes sexual spores. The molds are not an actual taxonomic or phylogenetic grouping – they can be found in the divisions Zygomycota, Deuteromycota or Ascomycota.

The presence of mold usually implies decay, although some molds are used deliberately in, for example cheese-making, and for the production of antibiotics.

The numerous spores released by mold does not cause direct harm in humans, but the hyphae grown from those spores could attach to cells along the respiratory tract and cause problems in those with weak immunity.

The mold Neurospora crassa is commonly used as a model organism in scientific experiments.