The present treatment constitutes a taxonomic study of the benthic marine red algae known in the northern Gulf of California. In all, 380 species of Rhodophyta belonging to two subphyla were found: the Rhodophytina represented by 2 classes, 2 orders, 2 families, 7 genera, and 14 species; and, the Eurhodophytina represented by 2 classes, 5 subclasses, 19 orders, 45 families, 132 genera, and 366 species. Of the red algae 67 are endemic species. Along with the 133 species of Chlorophyta and Phaeophyceae in the northern Gulf (Norris 2010) there are now 512 benthic marine macroalgal species known in the northern Gulf. The systematic account includes the accepted taxon name, descriptions of the subphyla, classes, orders, families, genera, and species of red algae presently known in the northern Gulf, with Keys to serve as a guide to their identification. Along with the current name for each species are its basionym, synonyms, type locality, relevant taxonomic studies, description, habitat, and distribution in the Gulf of California, and if applicable (i.e., not endemic) in the Eastern Pacific, Central Pacific, and/or Western Pacific. In addition to reviewing the taxonomic phycological literature pertinent to the Gulf of California and Pacific Mexico, several distribution extensions and new records are given. One new genus, one new subgeneric section, and eight new species are described. One new species name is given to replace an illegitimate name. Twenty-seven new combinations are made.