As the world’s food systems face unparalleled challenges from climate change, resources depletion, and population growth, crop wild relatives (CWRs) emerge as vital resources for enhancing climate resilience agriculture, food security and agricultural sustainability. Sustainable agriculture is achieved by the environmentally friendly farming practices that are resilient to climate change and capable of producing sufficient food with crop diversification, which promotes the cultivation of various crops to strengthen resilience against environmental changes. CWR are the species, which are closely related to crops, including their ancestors. CWRs are a critical resource for improving the resilience and productivity of modern agriculture, especially in the face of escalating challenges such as climate change, biodiversity loss, and population growth. They hold potential traits for crop improvement. However, use of CWRs is hindered by insufficient systematic conservation, largely due to their unclear identification. The rich genetic diversity present in CWRs, offers valuable traits like drought tolerance, pest and disease resistance, and enhanced nutritional quality that can be integrated into crop breeding programs to play a crucial role in addressing global food security challenges. This chapter provides a comprehensive overview of the CWRs role in supporting global food security. Furthermore, we discuss the importance of conservation strategies, international policy and breeding efforts that leverage CWRs to enhance climate resilience and agricultural sustainability.