Thirty-nine saxicolous species of Porina Müll. Arg. are recognized from the Southern Hemisphere. Their morphology is described, their affinities and distribution discussed and key to their identification provided. Most are illustrated. Zamenhofia Clauz. & Roux is considered to be synonymous with Porina. Twelve new species are described: P. aluniticola McCarthy, P. aptrootii McCarthy, P. crassa McCarthy, P. heterocarpa McCarthy, P. kantvilasii McCarthy, P. malmei McCarthy, P. papuensis McCarthy, P. partita McCarthy, P. psilocarpa McCarthy, P. riparia McCarthy, P. tasmanica McCarthy and P. weberi McCarthy. The following new combinations are proposed: P. ocellata (Malme) McCarthy (Thelenella ocellata Malme) and P. sagedioides (Zahlbr.) McCarthy (Clathroporina sagedioides Zahlbr.). Lectotypes are selected for P. africana var. basaltica Malme, P. curtula Malme, P. formosana Zahlbr., P. guaranitica Malme, P. melanops Malme, P. subpungens Malme and Verrucaria dolichophora Nyl. A new name, P. macroverrucosa McCarthy, is provided for the illegitimate P. depressula Zahlbr. A neotype is selected for P. subinterstes (Nyl.) Müll. Arg. Twenty-six names are placed in synonymy within Porina: P. formosana Zahlbr. and P. oceanica Räsänen [=P. bellendenica Müll. Arg.]; P. fernandeziana Zahlbr. [=P. chlorotica (Ach.) Müll. Arg.]; P. balanina Brusse and P. wilsoniana Müll. Arg. [=P. corrugata Müll. Arg.]; P. sceptrospora Vainio [=P. exserta Müll. Arg.]; P. heterospora (Fink) R. C. Harris and P. nucula var. granulatula (Nyl.) Zahlbr. [=P. guaranitica Malme]; P. eurysperma (Stizenb.) Zahlbr., P. knysnana Van der Byl ex Zahlbr. and P. saxicola (Knight) Müll. Arg. [=P. guentheri (Flotow.) Zahlbr.]; P. rufocarpella Zahlbr. [=P. leptalea (Durieu & Mont.) A. L. Sm.]; P. callosa (Krempelh.) Müll. Arg., P. elaeophaena (Krempelh.) Zahlbr., P. mastoidestera Müll. Arg., P. subpungens Malme and P. uruguayensis Räsänen [=P. mastoidea (Ach.) Müll. Arg.]; P. nigrofusca var. submersa Müll. Arg. [=P. nigrofusca Müll. Arg.]; P. africana var. basaltica Malme, P. astuta (Nyl.) Zahlbr., P. interstes (Nyl.) Harm., P. isidiophora Vainio, P. pertusarina * Zahlbr., P. tetracerae var. saxorum Zahlbr., P. tonduziana Müll. Arg. and P. variegata Fée [=P. tetracerae (Afz. in Ach.) Müll. Arg.]. Porina werthii (Zahlbr.) Zahlbr. is probably conspecific with P. chlorotica and the following are referable to other genera: P. chilensis (Dodge) Follmann [=Thelidium], P. decipiens Malme [=Strigula aff. stigmatella (Ach.) R. C. Hams], P. insueta (Nyl.) Müll. Arg. [?=Pyrenocollema], P. mahuana Dodge [ =Thelidium], P. macquariensis Dodge [?=Arthopyreniaceae] and P. rhodinula Zahlbr. [=S. affinis (Massal.) R. C. Harris].