Fungal-plant interactions are complex. Most exist for just a few brief days, while some continue over many months. During each interaction, a staggering repertoire of secreted biomolecules are produced by each fungal species to gain nutrients and to maintain the occupied niche by interfering with or suppressing plant defences and by producing antimicrobial compounds to ward off competitors. The secreted biomolecules now known to be required for pathogenesis (i.e. infection and disease formation) include small proteinaceous effectors, enzymes, accession proteins, simple and complex secondary metabolites and small interfering RNA molecules. The delivery of these biomolecules can occur directly from the growing filamentous or budding hyphae or alternatively from localized points of host contact where specialized infection structures such as haustoria or the biotrophy interface complex are formed. In this chapter, the secreted biomolecules produced by all the major biotrophic, necrotrophic and hemibiotrophic fungal species are described and inter-compared, along with the most frequently used experimental methods. This comprehensive interspecies comparison has provided several novel insights into fungal-plant interactions. For example, the classically cited lifestyle boundaries between non-haustoria-forming biotrophs and the necrotrophic or hemibiotrophic fungal pathogens are becoming increasingly difficult to uphold, including their modes of interaction with the host and the range of secreted biomolecules deployed, whereas a few previously recognized underpinning themes to pathogenicity involving secreted biomolecules remain intact. For example, most of the effectors found to be required for pathogenicity have a very limited taxon distribution. The secreted apoplastically accumulating small proteinaceous effectors tend to be cysteine rich, whereas those translocated and subsequently functioning in the plant cytoplasm are rarely cysteine rich. This review concludes with a short discussion of the perspectives for the biotechnological use of plant pathogen-derived secreted biomolecules for the pharmaceutical industry, sustainable food production, plant biomass utilization and green chemistries.