Technical Abstract: The soybean aphid (Aphis glycines Matsumura) is the most damaging insect pest of soybean [Glycine max (L.) Merr.] in North America. New soybean aphid biotypes have been evolving quickly and at least three confirmed biotypes have been reported in USA. These biotypes capable of defeating most of the known aphid resistant soybean genes indicate the need for identification of new genes. Plant Introduction (PI) 567301B was earlier identified to have antixenosis resistance against biotype 1 and 2 of the soybean aphid. Two hundred and three F7:9 recombinant inbred lines (RILs) developed from a cross of soybean aphid susceptible cultivar Wyandot and resistant PI 567301B were used for mapping aphid resistance genes using the quantitative trait loci (QTL) mapping approach. A genome wide molecular linkage map was constructed with 516 polymorphic SNP genotypes from 94 of the RILs and two candidate QTL regions (on chromosome 8 and 13) for aphid resistance were identified. Fine mapping of the QTL regions were conducted with SSR markers using all 203 RILs. A major gene on chromosome 13 was mapped near the previously identified Rag2 gene. However, a recent study revealed that the detached leaves of PI 567301B had no resistance against the soybean aphids while the detached leaves of PI 243540 (source of Rag2) maintained their aphid resistance. These results and the earlier finding that PI 243540 showed antibiosis resistance and PI 567301B showed antixenosis type resistance, suggest that the aphid resistances in the two PIs are not controlled by the same gene. Thus, we have mapped a new gene near the Rag2 locus or a new allele at the Rag2 locus for soybean aphid resistance that should be useful in breeding for new aphid resistant soybean cultivars. Publicly available molecular markers closely linked to this gene are available for marker assisted breeding. Also, the minor QTL found on chromosome 8 represents the first reported soybean aphid resistant locus on this chromosome