Plant growth-promoting fungi (PGPF) are rhizosphere-colonizing fungi that enhance plant health and productivity through mutualistic interactions. This diverse group encompasses various taxonomic genera including Aspergillus, Fusarium, Penicillium, Piriformospora, Phoma, Talaromyces, and Trichoderma, which thrive across ecological niches while benefiting their hosts. By co-evolving with plants, PGPF employ direct and indirect mechanisms to stimulate growth and development. Direct benefits include the mobilization of essential micro- and macronutrients, thereby promoting robust plant growth. Indirectly, PGPF synthesize defense-related enzymes, volatile organic compounds, and phytohormones, which suppress phytopathogens and bolster plant resilience against biotic and abiotic stressors. This chapter reviews recent advances in understanding plant–PGPF symbioses, emphasizing their role in enhancing nutrient acquisition, modulating phytohormone signaling, and inducing systemic resistance (ISR) to combat pathogen incursion. Furthermore, it explores the translational potential of PGPF in sustainable agriculture, highlighting their capacity to improve crop productivity and environmental stress tolerance through phytostimulation and integrated stress mitigation strategies. By bridging ecological insights with agricultural applications, this discussion underscores PGPF as pivotal agents in developing resilient, low-input agroecosystems.