This article outlines the important biogeochemical roles that fungi play in the degradation, utilization, and transformation of organic and inorganic substrates. Fungal populations are intimately involved in biogeochemical transformations at local and global scales and such processes have major implications for other living organisms, notably plant productivity and human health. While most prior attention has focussed on carbon and nitrogen cycling, the involvement of fungi in almost all other elemental cycles is emphasized. Some of these fungal transformations have beneficial applications in environmental biotechnology, for example, in metal leaching, recovery and detoxification, and xenobiotic and organic pollutant degradation. They may a...