Opium poppy (Papaver somniferum) is one of the world's oldest medicinal plants and a versatile model system to study secondary metabolism. However, our knowledge of its genetic diversity is limited, restricting utilization of the available germplasm for research and crop improvement. We used genotyping-by-sequencing to investigate the level of genetic diversity and population structure in a collection of poppy germplasm consisting of 91 accessions originating in 30 countries of Europe, North Africa, America, and Asia. We identified five genetically distinct subpopulations. Although the accessions were from geographically diverse regions, no strong association was detected between geographic origin and subpopulation at regional and sub-regional levels. However, most accessions obtained from the same country were grouped together as genetically distinct, likely a consequence of the restriction on movement of poppy germplasm. Phylogenetic analysis identified clades that were largely consistent with the subpopulations detected. Clades could be differentiated broadly based on capsule dehiscence, plant stature and seed weight, traits believed to be associated with poppy domestication. Our study determined that the genetically diverse collection was likely composed of both wild and cultivated forms. This has direct implications for germplasm management and utilization of the available diversity for genetic improvement of poppy.