Crop wild relatives (CWR) are species closely related to crop plants which can contribute beneficial traits, such as pest or disease resistance and yield improvement. These species are critical for improving agricultural production and increasing food security. They are also essential components of natural and semi-natural habitats as well as agricultural systems, and are therefore vital in maintaining ecosystem health. However, CWR, like any other group of wild species, are subject to an increasing range of threats: habitat loss, degradation and mismanagement, over-collection and climate change. Through an examination of the national, regional and global context of CWR, these authoritative studies present methodologies and case studies that review and provide recommendations for global conservation and use. Topics range from the establishment of conservation priorities and strategies, threat assessment and genetic erosion and pollution.