A revision of the genus Parmotrema (Ascomycotina: Parmeliaceae) in Papua New Guinea has shown it to comprise 50 species. Twelve species are new records for Papua New Guinea and six are described as new to science: Parmotrema kurolawianum, P. malonprotocetraricum, P. menyamyaense, P. sipmanii, P. verrucatum and P. watutense. The new combination Parmotrema proeinsuetum (Hale) Louwhoff & Elix is made. Fourteen of the 50 species of Parmotrema are considered endemic to Papua New Guinea. A key and descriptions of the species are given, and the synonymy, chemistry, distribution, ecology and taxonomic affinities of each species discussed. In addition, three species of Rimelia and one of Canomaculina have been identified for Papua New Guinea, and these are also described.