Fungi comprise 1, 2, 3, ..., or maybe around 5.1 million species? Even scientists do not currently agree on how many fungi species may be found on planet Earth, with only around 120,000 having been described so far. Fungi have been classified as a separate kingdom of organisms, as complex and diverse as plants and animals, of which only a few percent have been named and described. Fungal biomasses and fungal metabolites share a long common history with human and animal nutrition and health. Macrofungi and filamentous fungi constitute a large portfolio of proteins, lipids, vitamins, minerals, oligo elements, pigments, colorants, bioactive compounds, antibiotics, pharmaceuticals, etc. For example, industrially important enzymes and microbial biomass proteins have been produced from fungi for more than 50 years. Some start-ups convert byproducts and side streams rich in carbohydrates into a protein-rich fungal biomass. This biomass can then be processed into a vegan meat substitute for food applications. In recent years, there has also been a significant increase (in fact, a significant revival) in the number of publications in the international literature dealing with the production of lipids by microbial sources (the single-cell oils (SCO) that are produced by the so-called “oleaginous”microorganisms, including “oleaginous”fungi such as zygomycete species, e.g., Cunninghamella echinulata and Mortierella isabellina). Fungi are potential sources of polyunsaturated fatty acids (PUFA), as these microorganisms can accumulate large amounts of high-valued PUFAs, such as gamma-linolenic acid (GLA) and arachidonic acid (ARA). The purpose of this Special Issue of Journal of Fungi (MDPI) was not to provide a comprehensive overview of the vast arena of how fungi and fungal metabolites are able to improve human and animal nutrition and health; rather, we, as Guest Editors, wished to encourage authors working in this field to publish their most recent work in this rapidly growing journal in order for the large readership to appreciate the full potential of wonderful and beneficial fungi. Thus, this Special Issue welcomed scientific contributions on applications of fungi and fungal metabolites, such as bioactive fatty acids, pigments, polysaccharides, alkaloids, terpenoids, etc., with great potential in human and animal nutrition and health.