Filamentous fungi are an amazing group of microorganisms able to both degrade and produce a plethora of different compounds. Many fungi have rather modest nutritional requirements, making them very interesting for biotechnological applications, with applications in both submerged and solid-state fermentation. Applications include agriculture, food, and feed, pharmaceutical, pulp and paper, textile industries, as well as a potential for waste valorization. Some of the current and potential products include: ethanol, citric acid, gluconic acid, itaconic acid, lactic acid, fumaric acid, and the fungal biomass as a food or feed, as well as more specific compounds such as enzymes.