Climate change is predicted to have far-reaching deleterious impacts worldwide; agriculture in particular is expected to be effected by significant loss of suitable land and crop yields in the world’s most populous and poorest regions. Crop wild relatives (CWR) are a rich source of underutilised genetic diversity which could help to mitigate climate change for agriculture through breeding new resilient varieties. However, CWR are under-conserved and threatened in the wild. This thesis researches and develops systematic methodologies to advance knowledge and support action on in situ CWR conservation at the global level. Methods included developing a global inventory of CWR associated with crops important for food security worldwide, species distribution modelling, climate change analysis, in situ gap analysis, reserve planning and prioritisation, and, examining the congruence of CWR distributions with regions of high biodiversity and crop diversity. The methods described here can be applied to CWR at both the national and regional level to ensure robust in situ CWR conservation. A principal success of this research is the global CWR inventory, which has been used in several national strategies and as the basis of a major ex situ germplasm collection mission worldwide.