Nanotechnology has emerged as a transformative force in modern agriculture, offering innovative solutions to long-standing challenges in crop protection. This chapter explores the role of nanotechnology, particularly nanofungicides, in advancing sustainable plant disease management. Nanofungicides overcome the main drawbacks of traditional fungicides, such as environmental persistence, low bioavailability, and non-target toxicity, by utilizing the special physicochemical characteristics of materials at the nanoscale, such as increased surface area, enhanced reactivity, and controlled release. These nanoformulations enable precise targeting of fungal pathogens, improved adhesion to plant surfaces, and reduced chemical inputs, thereby enhancing effectiveness while minimizing ecological disruption. However, their integration into agroecosystems raises concerns about potential impacts on the plant microbiome, soil health, and non-target organisms. This chapter provides a comprehensive overview of nanofungicide classifications, mechanisms of action, and interactions with plant–microbe systems, alongside a critical examination of their benefits, risks, and future potential. Ultimately, nanotechnology holds significant promise for driving sustainable agriculture, but responsible development, regulatory oversight, and interdisciplinary research are essential to ensure its safe and equitable application.