Leaf rust (LR) caused by Puccinia triticina, is an important foliar disease of wheat (Triticum aestivum L.) and the deployment of resistant cultivars is the most viable control strategy. However, P. triticina has the ability to rapidly overcome resistance genes, thus breeders require a constant supply of new sources of resistance. In this study we evaluated a diversity panel of 295 bread wheat accessions from N. I. Vavilov Institute of Plant Genetic Resources (VIR) in St Petersburg, Russia, for LR resistance and performed genome-wide association study (GWAS) using 8, 900 polymorphic DArTseq-GBS markers. The diversity panel was evaluated in 11 environments using three LR pathotypes, prevalent in Australia. GWAS identified a total of 52 significant marker-trait associations representing 34 independent quantitative trait loci (QTL). Among them, 32 QTL were associated with adult plant resistance (APR). Of the 34 QTL, 15 were considered novel and six co-located with the catalogued Lr genes. Further, 13 of the predicted QTLs aligned with regions reported in recent GWAS studies. One major, seedling LR resistance QTL located on chromosome 3A with high linkage disequilibrium among markers, suggested a high allelic fixation. Subsequent haplotype analysis found seven variants, of which two were strongly associated with increased LR resistance at seedling stage. Similarly, analysis of an APR QTL on chromosome 7B depicted 22 variants, of which two were associated with adult LR resistance. Furthermore, we observed that most of the tested accessions from our diversity panel carried 10 or more combined resistance-related marker alleles. Also, additive effect of favorable alleles and LR resistance was evident, highlighting the potential of allele stacking for a sustainable LR resistance improvement. The QTLs identified in this study represent a useful basis for introgression of promising new resistance factors into modern germplasm to achieve a sustained control of LR in wheat.