Suillus quiescens sp. nov. is common under Pinus muricata on Santa Cruz and Santa Rosa Islands in the northern Channel Islands of California, and we subsequently found it fruiting at Point Reyes National Seashore on the central coast of California. Sequences from the internal transcribed spacer region show that it is distinct from all 44 species of Suillus tested, and features of its morphology separate it from all other unsequenced species. Suillus quiescens has a broader distribution than coastal California because it also was encountered as ectomycorrhizae on roots of pine seedlings from the eastern Sierra Nevada, coastal Oregon and the southern Cascade Mountains. The reason it had not been identified from these areas might be due to its resemblance to S. brevipes at maturity or it might be a rare fruiter that persists in the spore bank.