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 element cycling at local and global scales and such processes have major implications for living organisms, notably plant productivity and human health. While most attention has focussed on carbon cycling, the involvement of fungi in most other elemental cycles is emphasised. Some fungal transformations have applications in environmental biotechnology, e.g. in metal leaching, recovery and detoxification, xenobiotic and organic pollutant degradation, as well as result in adverse effects when these mechanisms are involved in degradation of foodstuffs, natural products and building materials. This account highlights the interdisciplinary approach that is necessary to further understanding of the important roles that fungi play in the biogeochemical cycling of elements, the chemical and biological mechanisms that are involved, and their biotechnological significance.