San Bernardino National Forest in southern California encompasses two major mountain ranges, the San Bernardino Mountains and the San Jacinto Mountains. Here 414 taxa of lichenized fungi are reported from San Bernardino National Forest as a whole; 327 from the San Jacinto Mountains (including the Santa Rosa Mountains), and 289 from the San Bernardino Mountains. Two species new to science are described: Lecanora remota and Lecidea stratura. Two undescribed taxa of Bellemerea and Scytinium are reported, both currently under study. Five species are reported new for North America and California: Gloeoheppia rugosa, Lecanora formosa, Peccania cernohorskyi, P. corallina and Psorotichia vermiculata. Peccania cernohorskyi is also reported new for Canada (British Columbia). Eight species are reported new for California: Caloplaca diphasia, C. isidiigera, Peltigera extenuata, Rhizocarpon simillimum, Rinodina lobulata, R. terrestris, Sarcogyne squamosa, and Xylographa difformis. Lecidea xanthococcoides is recognized as a synonym of Lecanora cadubriae. The California endemic Lecidea kingmanii is reported as producing 4-0-demethylplanaic acid. Polysporina simplex is treated as Acarospora simplex and P. urceolata as A. urceolata. The new combination Acarospora gyrocarpa is proposed for Polysporina gyrocarpa.