Palmaria hecatensis sp. nov. is described based on material from northern British Columbia. Male gametophytes and tetrasporophytes are thick, coriaceous, flattened blades, linear to lobed in habit and arise from an extensive encrusting basal holdfast. Putative female gametophytes are microscopic multicellular discs. Palmaria hecatensis grows on rocky shores in the midintertidal to lower intertidal zones and has a known geographical distribution from Nootka Island, Vancouver Island, B.C., to Shemya Island in the Aleutian Islands, Alaska. Palmaria hecatensis is compared with other species in the genus and, in addition, another distinctive (and possibly undescribed) Palmaria species from British Columbia and Alaska is discussed, bringing the total number of Palmaria species reported in the North Pacific Ocean to six.