Technical Abstract: Edible European pears (Pyrus communis subsp. communis L.) are derived from wild relatives native to the Caucasus Mountain region and Eastern Europe. Microsatellite markers (13 loci) were used to determine the relationships among 145 wild and cultivated individuals of P. communis maintained in the National Plant Germplasm System (NPGS). A Bayesian clustering method grouped the individual pear genotypes into 12 clusters. P. communis subsp. caucasica (Fed.) Browicz, native to the Caucasus Mountains of Russia, Crimea, and Armenia can be genetically differentiated from P. communis subsp. pyraster L. native to Eastern European countries including Macedonia, Moldova, Poland, and Turkey. The domesticated pears cluster closely together and are most closely related to a group of genotypes that are intermediate to the P. communis subsp. pyraster and the P. communis subspecies caucasica groups. Based on the high number of unique alleles and heterozygosity in each of the 12 clusters, we conclude that genetic diversity of wild P. communis is not fully represented at the NPGS. Additional diversity may be present in seed accessions stored in the NPGS and more Pyrus diversity could be captured through supplementary collection trips to Eastern Europe, the Caucasus Mountains, and the surrounding countries.