Leaf rust, caused by Puccinia triticina Eriks. (Pt = P. recondita Rob. Ex Desmaz. F. sp. tritici), is an economically significant pathogen affecting durum wheat (Triticum turgidum var. durum L.) crops worldwide. Genetic resistance is one of the most effective and environmentally friendly methods to control leaf rust in wheat. New sources of resistance genes need to be identified due to the threat of new Pt races to durum wheat production. Marker assisted selection (MAS) is a highly efficient method to select resistance genes in breeding programs particularly to pyramid multiple resistance genes in new varieties. The objective of this study was to characterize and map leaf rust resistance genes in a Canadian durum wheat Strongfield. A double haploid (DH) mapping population of 87 DH lines was developed from the cross Strongfield/Blackbird. Seedling rust tests with Pt isolates 12-3 MBDS, 06-1-1 TDBG, 128-1 MBRJ, 74-2 MGBJ, and 77-2 TJBJ revealed a single hypersensitive leaf rust resistance gene. Three genes segregated for resistance to isolate 1-1 BBBD at the seedling stage, one of which controlled resistance to the other five Pt isolates. Blackbird contributed one of the seedling resistance genes effective against isolate 1-1 BBBD. Parental lines and 87 DH lines were genotyped using the Illumina Infinium assay with the iSelect 90K wheat SNP array. A database search using the DNA sequences of linked markers provided a putative location in the Chinese Spring reference genome sequence. The gene conferring resistance to the six isolates used in the study mapped to the long arm of chromosome 3A and was temporarily designated as LrStr_3A. No leaf rust resistance gene has been detected in this region previously. Quantitative trait locus (QTL) analysis identified eight QTL controlling leaf rust resistance in field leaf rust nurseries. One of these QTL mapped to chromosome 3AL as the same region of LrStr_3A. Another QTL mapped to the expected location of the adult plant resistance (APR) gene Lr46 based upon the marker csLV46G22. Kompetitive allele-specific PCR (KASP) markers were developed for LrStr_3A that will be useful for MAS.