Rust disease, a plant disease caused by various species of fungi, is commonly spotted by its unique brown-hued spore pattern. Readers curious about the plant pathogens that cause the disease may enjoy this comprehensive key. Globally, thousands of species of rust fungi exist. More than 500 of these species hail from South Africa, giving the area a unique lens into rust fungi classification and identification. The key is both collaborative and on-going, inviting users to contribute specimens and resources, with a focus on adding additional taxa as available. Users may also enjoy the Identify a Rust Fungus tool, which provides various filters to narrow down different specimens one might encounter. The project is a collaboration between the Forestry Agricultural Biotechnology Institute (University of Pretoria, South Africa), the Department of Agriculture and Forestry (Queensland Government, Australia), and the Queensland Alliance for Agriculture and Food Innovation (University of Queensland, Australia). The key is authored by Dr. Alistair McTaggart (University of Pretoria) and Dr. Dean Beasley (Queensland Department of Agriculture and Fisheries, Ecosciences Precinct) with additional contributions from other scholars.