In the Pacific Northwest, yellow chanterelles have long been referred to as Cantharellus cibarius, synonymous with the European yellow chanterelle. Broad scale genetic surveys of North American chanterelles with C. cibarius-like morphology have demonstrated that the nrDNA internal transcribed spacer exhibits length variability, suggesting that this common morphology masks a species complex. Recently researchers have used morphological and genetic data to identify the yellow chanterelle most frequently harvested from American Pacific Northwest forests as C. formosus, a species once thought to be rare in the region. We present three genetic data sets and one morphological data set that characterize a previously undescribed, species of yellow chanterelle from the central Cascade Mountains of Oregon. Phylogenetic analyses of the nrDNA large subunit and ITS regions show that C. cascadensis sp. nov., along with two other yellow chanterelle taxa (C. cibarius var. roseocanus and European C. cibarius), are more closely related to white chanterelles (C. subalbidus) than they are to C. formosus. Data from five microsatellite loci provide evidence that C. formosus, C. subalbidus, and C. cascadensis sp. nov. do not interbreed when they co-occur spatially and temporally in Douglas fir-western hemlock forests. This demonstrates that these three sympatric chanterelles are biological species with boundaries congruent with those delineated by nrDNA phylogenetic clades. Morphological data indicate that the colour of the pileus and shape of the stipe can be used to separate fresh collections of the two yellow species now known to co-occur in Douglas fir-western hemlock forests in Oregon.