A revisionary synopsis is presented for the family Trypetheliaceae, based on a separately published phylogenetic analysis of a large number of species, morpho-anatomical and chemical study of extensive material, and revision of numerous type specimens. A total of 418 species is formally accepted in this synopsis, distributed among 15 genera as follows: Aptrootia (3), Architrypethelium (7), Astrothelium (242), Bathelium (16), Bogoriella (29), Constrictolumina (9), Dictyomeridium (7), Distothelia (3), Marcelaria (3), Nigrovothelium (2), Novomicrothelia (1), Polymeridium (50), Pseudopyrenula (20), Trypethelium (16), and Viridothelium (10). All accepted genera, including new genera described separately in this issue, are keyed out and briefly described and discussed, and keys are provided for all accepted species within each genus. Entries with full synonymy and brief descriptions, and in part also discussions, are provided for all accepted species, except those newly described elsewhere in this issue, which are cross-referenced in the corresponding keys. The description of the newly defined genera takes into account phylogeny in combination with morpho-anatomical features with the result that they are mostly recognizable by a combination of thallus, ascoma and ascospore features. Most species previously assigned to the genera Astrothelium, Campylothelium, Cryptothelium, and Trypethelium, based on a schematic concept of ascoma morphology and ascospore septation, are now included in a single genus, Astrothelium, with highly variable ascoma morphology and ascospore septation but invariably with astrothelioid ascospores (at least when young), that is diamond-shaped lumina, and a well-developed, corticate, usually olive-green thallus that often covers the ascomata. While the genera Aptrootia (large, brown, muriform ascospores), Architrypethelium (large, mostly 3-septate ascospores), and Pseudopyrenula (ecorticate, white thalli and astrothelioid ascospores) are maintained, Trypethelium is redefined to include species with raised, pseudostromatic ascomata and multiseptate ascospores with thin septa. The sister group of Trypethelium is the genus Marcelaria, with brightly coloured pseudostromata and muriform ascospores. Bathelium is now limited to species with strongly raised, fully exposed pseudostromata and septate to muriform ascospores with thin septa. Several genera are recognized for more basal lineages with mostly ecorticate, white thalli and solitary, exposed ascomata previously assigned to Arthopyrenia, Mycomicrothelia and Polymeridium, viz. Bogoriella, Constrictolumina, Dictyomeridium, and Novomicrothelia. In addition, separate genera are accepted for the Trypethelium tropicum (Nigrovothelium) and T. virens (Viridothelium) groups. In addition, a refined species concept resulting from phylogenetic studies is employed which pays particular attention to morphological features of the thallus and ascomata. Of a total of 526 names checked, 107 remain synonyms of accepted names and a further eight are newly excluded from the family. Based on these redispositions, the following 146 new combinations are proposed, including reinstatement of numerous names previously subsumed into synonymy: Architrypethelium columbianum (Nyl.) Aptroot & Lücking comb. nov., A. grande (Kremp.) Aptroot & Lücking comb. nov., Astrothelium aeneum (Eschw.) Aptroot & Lücking comb. nov., A. alboverrucum (Makhija & Patw.) Aptroot & Lücking comb. nov., A. amazonum (R. C. Harris) Aptroot & Lücking comb. nov., A. ambiguum (Malme) Aptroot & Lücking comb. nov., A. andamanicum (Makhija & Patw.) Aptroot comb. nov., A. annulare (Spreng.) Aptroot & Lücking comb. nov., A. aurantiacum (Makhija & Patw) Aptroot & Lücking comb. nov., A. auratum (R. C. Harris) Aptroot & Lücking comb. nov., A. aureomaculatum (Vain.) Aptroot & Lücking comb. nov., A. basilicum (Kremp.) Aptroot & Lücking comb. nov., A. bicolor (Taylor) Aptroot & Lücking comb. nov., A. buckii (R. C. Harris) Aptroot & Lücking comb. nov., A. calosporum (Müll. Arg.) Aptroot & Lücking comb. nov., A. cartilagineum (Fée) Aptroot & Lücking comb. nov., A. cecidiogenum (Aptroot & Lücking) Aptroot & Lücking comb. nov., A. ceratinum (Fée) Aptroot & Lücking comb. nov., A. chapadense (Malme) Aptroot & Lücking comb. nov., A. chrysoglyphum (Vain.) Aptroot & Lücking comb. nov., A. chrysostomum (Vain.) Aptroot & Lücking comb. nov., A. cinereorosellum (Kremp.) Aptroot & Lücking comb. nov., A. cinereum (Müll. Arg.) Aptroot & Lücking comb. et stat. nov., A. confluens (Müll. Arg.) Aptroot & Lücking comb. nov., A. consimile (Müll. Arg.) Aptroot & Lücking comb. nov., A. deforme (Fée) Aptroot & Lücking comb. nov., A. defossum (Müll. Arg.) Aptroot & Lücking comb. nov., A. degenerans (Vain.) Aptroot & Lücking comb. nov., A. dissimilum (Makhija & Patw.) Aptroot & Lücking comb. nov., A. effusum (Aptroot & Sipman) Aptroot & Lücking comb. nov., A. endochryseum (Vain.) Aptroot & Lücking comb. nov., A. exostemmatis (Müll. Arg.) Aptroot & Lücking comb. nov., A. feei (C. F. W. Meissn.) Aptroot & Lücking comb. nov., A. ferrugineum (Müll. Arg.) Aptroot & Lücking comb. nov., A. galligenum (Aptroot) Aptroot & Lücking comb. nov., A. gigantosporum (Müll. Arg.) Aptroot & Lücking comb. nov., A. indicum (Upreti & Ajay Singh) Aptroot & Lücking comb. nov., A. infossum (Nyl.) Aptroot & Lücking comb. nov., A. infuscatulum (Müll. Arg.) Aptroot & Lücking comb. nov., A. irregulare (Müll. Arg.) Aptroot & Lücking comb. nov., A. keralense (Upreti & Ajay Singh) Aptroot & Lücking comb. nov., A. kunzei (Fée) Aptroot & Lücking comb. nov., A. leioplacum (Müll. Arg.) Aptroot & Lücking comb. nov., A. lugescens (Nyl.) Aptroot & Lücking comb. nov., A. luridum (Zahlbr.) Aptroot & Lücking comb. nov., A. macrocarpum (Fée) Aptroot & Lücking comb. nov., A. macrosporum (Makhija & Patw.) Aptroot & Lücking comb. nov., A. marcidum (Fée) Aptroot & Lücking comb. nov., A. megaleium (Kremp.) Aptroot & Lücking comb. nov., A. megalophthalmum (Müll. Arg.) Aptroot & Lücking comb. nov., A. megalostomum (Vain.) Aptroot & Lücking comb. nov., A. megaspermum (Mont.) Aptroot & Lücking comb. nov., A. meiophorum (Nyl.) Aptroot & Lücking comb. nov., A. meristosporoides (P. M. McCarthy & Vongshew.) Aptroot & Lücking comb. nov., A. meristosporum (Mont. & Bosch) Aptroot & Lücking comb. nov., A. neogalbineum (R. C. Harris) Aptroot & Lücking comb. nov., A. nigratum (Müll. Arg.) Aptroot & Lücking comb. et stat. nov., A. nigrorufum (Makhija & Patw.) Aptroot & Lücking comb. nov., A. nitidiusculum (Nyl.) Aptroot & Lücking comb. nov., A. octosporum (Vain.) Aptroot & Lücking comb. nov., A. oligocarpum (Müll. Arg.) Aptroot & Lücking comb. nov., A. olivaceofuscum (Zenker) Aptroot & Lücking comb. nov., A. papillosum (P. M. McCarthy) Aptroot & Lücking comb. nov., A. papulosum (Nyl.) Aptroot & Lücking comb. nov., A. peranceps (Kremp.) Aptroot & Lücking comb. nov., A. phaeothelium (Nyl.) Aptroot & Lücking comb. nov., A. phlyctaenua (Fée) Aptroot & Lücking comb. nov., A. porosum (Ach.) Aptroot & Lücking comb. nov., A. praetervisum (Müll. Arg.) Aptroot & Lücking comb. nov., A. pseudoplatystomum (Makhija & Patw.) Aptroot & Lücking comb. nov., A. pseudovariatum (Upreti & Ajay Singh) Aptroot & Lücking comb. nov., A. puiggarii (Müll. Arg.) Aptroot & Lücking comb. nov., A. pulcherrimum (Fée) Aptroot & Lücking comb. nov., A. pupula (Ach.) Aptroot & Lücking comb. nov., A. purpurascens (Müll. Arg.) Aptroot & Lücking comb. nov., A. pustulatum (Vain.) Aptroot & Lücking comb. nov., A. rufescens (Müll. Arg.) Aptroot & Lücking comb. et stat. nov., A. sanguinarium (Malme) Aptroot & Lücking comb. nov., A. santessonii (Letr.-Gal.) Aptroot & Lücking comb. nov., A. saxicola (Malme) Aptroot & Lücking comb. nov., A. scoria (Fée) Aptroot & Lücking comb. nov., A. scorizum (Müll. Arg.) Aptroot & Lücking comb. nov., A. sierraleonense (C. W. Dodge) Aptroot & Lücking comb. nov., A. sikkimense (Makhija & Patw.) Aptroot & Lücking comb. nov., A. spectabile (Aptroot & Ferraro) Aptroot & Lücking comb. nov., A. sphaerioides (Mont.) Aptroot & Lücking comb. nov., A. stramineum (Malme) Aptroot & Lücking comb. nov., A. straminicolor (Nyl.) Aptroot & Lücking comb. nov., A. subcatervarium (Malme) Aptroot & Lücking comb. nov., A. subdiscretum (Nyl.) Aptroot & Lücking comb. nov., A. subdisjunctum (Müll. Arg.) Aptroot & Lücking comb. nov., A. subdissocians (Nyl. ex Vain.) Aptroot & Lücking comb. et stat. nov., A. superbum (Fr.) Aptroot & Lücking comb. nov., A. tenue (Aptroot) Aptroot & Lücking comb. nov., A. thelotremoides (Nyl.) Aptroot & Lücking comb. nov., A. trypethelizans (Nyl.) Aptroot & Lücking comb. nov., A. tuberculosum (Vain.) Aptroot & Lücking comb. nov., A. ubianense (Vain.) Aptroot & Lücking comb. nov., A. variatum (Nyl.) Aptroot & Lücking comb. nov., A. vezdae (Makhija & Patw.) Aptroot & Lücking comb. nov., Bathelium austroafricanum (Zahlbr.) Aptroot & Lücking comb. nov., B. nigroporum (Makhija & Patw.) Aptroot & Lücking comb. nov., Bogoriella alata (Groenh. ex Aptroot) Aptroot & Lücking comb. nov., B. annonacea (Müll. Arg.) Aptroot & Lücking comb. nov., B. apposita (Nyl.) Aptroot & Lücking comb. nov., B. captiosa (Kremp.) Aptroot & Lücking comb. nov., B. collospora (Vain.) Aptroot & Lücking comb. nov., B. confluens (Müll. Arg.) Aptroot & Lücking comb. nov., B. conothelena (Nyl.) Aptroot & Lücking comb. nov., B. decipiens (Müll. Arg.) Aptroot & Lücking comb. nov., B. exigua (Müll. Arg.) Aptroot & Lücking comb. nov., B. fumosula (Zahlbr.) Aptroot & Lücking comb. nov., B. hemisphaerica (Müll. Arg.) Aptroot & Lücking comb. nov., B. lateralis (Sipman) Aptroot & Lücking comb. nov., B. leuckertii (D. Hawksw. & J. C. David) Aptroot & Lücking comb. nov., B. macrocarpa (Komposch, Aptroot & Hafellner) Aptroot & Lücking comb. nov., B. megaspora (Aptroot & M. Cáceres) Aptroot & Lücking comb. nov., B. miculiformis (Nyl. ex Müll. Arg.) Aptroot & Lücking comb. nov., B. minutula (Zahlbr.) Aptroot & Lücking comb. nov., B. modesta (Müll. Arg.) Aptroot & Lücking comb. nov., B. nonensis (Stirt.) Aptroot & Lücking comb. nov., B. obovata (Stirt.) Aptroot & Lücking comb. nov., B. pachytheca (Sacc. & Syd.) Aptroot & Lücking comb. nov., B. punctata (Aptroot) Aptroot & Lücking comb. nov., B. queenslandica (Müll. Arg.) Aptroot & Lücking comb. nov., B. socialis (Zahlbr.) Aptroot & Lücking comb. nov., B. striguloides (Sérus. & Aptroot) Aptroot & Lücking comb. nov., B. subfallens (Müll. Arg.) Aptroot & Lücking comb. nov., B. thelena (Ach.) Aptroot & Lücking comb. nov., B. triangularis (Aptroot) Aptroot & Lücking comb. nov., B. xanthonica (Komposch, Aptroot & Hafellner) Aptroot & Lücking comb. nov., Constrictolumina esenbeckiana (Fée) Lücking, M. P. Nelsen & Aptroot comb. nov., C. leucostoma (Müll. Arg.) Lücking, M. P. Nelsen & Aptroot comb. nov., C. lyrata (R. C. Harris) Lücking, M. P. Nelsen & Aptroot comb. nov., C. majuscula (Nyl.) Lücking, M. P. Nelsen & Aptroot comb. nov., C. malaccitula (Nyl.) Lücking, M. P. Nelsen & Aptroot comb. nov., C. porospora (Vain.) Lücking, M. P. Nelsen & Aptroot comb. nov., Dictyomeridium amylosporum (Vain.) Aptroot, M. P. Nelsen & Lücking comb. nov., D. campylothelioides (Aptroot & Sipman) Aptroot, M. P. Nelsen & Lücking comb. nov., D. immersum (Aptroot, A. A. Menezes & M. Cáceres) Aptroot, M. P. Nelsen & Lücking comb. nov., D. isohypocrellinum (Xavier-Leite, M. Cáceres & Aptroot) Aptroot, M. P. Nelsen & Lücking comb. nov., D. paraproponens (Aptroot, M. Cáceres & E. L. Lima) Aptroot, M. P. Nelsen & Lücking comb. nov., Distothelia rubrostoma (Aptroot) Aptroot & Lücking comb. nov., Phyllobathelium chlorogastricum (Müll. Arg.) Aptroot & Lücking comb. nov., Pseudopyrenula cubana (Müll. Arg.) Aptroot & Lücking comb. nov., Viridothelium cinereoglaucescens (Vain.) Lücking, M. P. Nelsen & Aptroot comb. nov., V. indutum (Stirt.) Aptroot & Lücking comb. nov., and V. megaspermum (Makhija & Patw.) Aptroot & Lücking comb. nov. In addition, six replacement names are proposed: Astrothelium campylocartilagineum Aptroot & Lücking nom. nov., A. grossoides Aptroot & Lücking nom. nov., A. octosporoides Aptroot & Lücking nom. nov., A. scoriothelium Aptroot & Lücking nom. nov., A. pyrenastrosulphureum Aptroot & Lücking nom. nov., and Bathelium pruinolucens Aptroot & Lücking nom. et stat. nov. Along with this, 57 lectotypes are newly designated. Most species (392 out of 418) are illustrated, with a total of 697 images in 59 plates, including 406 type specimens. Where appropriate, taxa are briefly discussed. New country or continental records are listed for many species in their revised circumscription. A checklist of taxa described or placed in genera belonging in Trypetheliaceae but previously excluded from the family, and their current names, is also provided.