The article discusses the importance and role of fungal directfed microbials (DFM) and anaerobic rumen fungi (ARF) in ruminants and their metabolic pathways of plant fibre decomposition, as well as rumen fermentation processes. ARF classification, enzymatic activity, impact on rumen metabolism, as well as fungal DFM and application of their metabolites in ruminant feeding are presented. The research area concerning ARF in ruminant feeding is gaining interest as the subject is still poorly elucidated. The latest research in the field of ruminant physiology and nutrition has pointed to a significant impact of ARF and fungal DFM on nutrient degradability, fermentation profile in the rumen, and animal performance. Although, the proportion of fungi in the total rumen microorganisms is low (approximately 8% of rumen biomass), they play a crucial role in generating a series of enzymes utilising difficult-to-debase compounds, such as cellulose, hemicelluloses and xylose. Although enzymes secreted by ARF are not able to degrade lignin, they can solubilise lignocellulosic complexes and expand the surface area for enzymatic activity. This leads to a better utilisation of fibrous feeds, increased nutrient digestibility, and enhanced rumen fermentation. A comprehensive description and discussion of these issues in the review provides an in-depth look at the role of ARF and the potential use of ARF as DFM in the ruminant nutrition in a-broad perspective.