Melanins are ancient biological pigments found in all kingdoms of life. In fungi, their role in microbial pathogenesis is well established; however, these complex biomolecules also confer upon fungal microorganisms the faculty to tolerate extreme environments such as the Earth's poles, the International Space Station and places contaminated by toxic metals and ionizing radiation. A remarkable property of melanin is its capacity to interact with a wide range of electromagnetic radiation frequencies, functioning as a protecting and energy harvesting pigment. Other roles of fungal melanin include scavenging of free radical, thermo-tolerance, metal ion sequestration, cell development, and mechanical-chemical cellular strength. In this review, we explore the various functions ascribed to this biological pigment in fungi and its remarkable physicochemical properties. Functions of fungal melanin. Fungal melanins play multiple biological functions including photoprotection, energy harvest and thermoregulation by readily absorbing and transducing electromagnetic radiation. Fungal melanins also function in free radical and metal binding; protection against dehydration, chemical and mechanical stressors; and fungal development and conidiation. Display omitted •Melanins play multiple ecological and biochemical functions in living organisms.•Black fungi are polyextremophiles.•Fungal melanins protect against many physical and chemical environmental stressors.•The physicochemical properties of fungal melanins many differ among species.