<p>Weeds pose a significant threat to ecological stability and agricultural productivity by disrupting ecosystem balance and competing with crop plants for essential resources. Chemical herbicides are an integral part of conventional weed management; however, their long-term and reckless application has resulted in environmental contamination, chemical accumulation in agricultural crops, and the emergence of resistant phytopathogens, underscoring the need for sustainable alternatives. Weeds are an underutilized bioresource that contains antifungal phytochemicals that can be used to develop plant-based biofungicides. This review highlights the role of weed-derived biofungicides and the use of nanotechnology as a novel approach to improving antifungal efficacy and reducing chemical use. By employing controlled-release mechanisms, green manufacturing of nanoparticles from weed extracts enhances the stability, bioavailability, and targeted delivery of antifungal chemicals. Nanofungicides and nanoherbicides are nano-enabled formulations that provide increased efficacy against phytopathogens while reducing environmental impact. This review emphasizes promising strategies for sustainable disease management and ecological conservation by integrating weed use, biofungicide development, and nanotechnology-based interventions, thereby supporting resilient and sustainable agricultural systems.</p> Graphical abstract <p></p>