﻿AbstractThe Southeast Asian genusAngustopila, currently comprising 13 nominal species, encompasses the world’s tiniest land snails. This work shows that there are far more species than previously suspected, and that this genus is in fact, a very speciose group of tiny snails widely distributed in Southeast Asia.Angustopilais revised based on type material of known species as well as 211 samples newly collected in China, Laos, Myanmar, Thailand and Vietnam. Altogether, 53 species and one subspecies are recognised, of which 42 species and subspecies are new to science:A.akrodonPáll-Gergely & Hunyadi,sp. nov.,A.apiariaPáll-Gergely & Hunyadi,sp. nov.,A.apiostomaPáll-Gergely & Vermeulen,sp. nov.,A.apokritodonPáll-Gergely & Hunyadi,sp. nov.,A.antidomedonPáll-Gergely & Hunyadi,sp. nov.,A.babelPáll-Gergely & Vermeulen,sp. nov.,A.bathyodonPáll-Gergely & Hunyadi,sp. nov.,A.bidentataPáll-Gergely & Jochum,sp. nov.,A.cavicolaPáll-Gergely & Dumrongrojwattana,sp. nov.,A.cicatricosaPáll-Gergely & Vermeulen,sp. nov.,A.coprologosuninodusPáll-Gergely & Grego,ssp. nov.,A.erawanicaPáll-Gergely & Dumrongrojwattana,sp. nov.,A.fratermajorPáll-Gergely & Vermeulen,sp. nov.,A.fraterminorPáll-Gergely & Vermeulen,sp. nov.,A.gracilisPáll-Gergely & Hunyadi,sp. nov.,A.halongensisPáll-Gergely & Vermeulen,sp. nov.,A.hyronPáll-Gergely & Vermeulen,sp. nov.,A.maasseniPáll-Gergely & Vermeulen,sp. nov.,A.majusculaPáll-Gergely & Hunyadi,sp. nov.,A.margaritarionPáll-Gergely & Hunyadi,sp. nov.,A.megastomaPáll-Gergely & Vermeulen,sp. nov.,A.occidentalisPáll-Gergely & Hunyadi,sp. nov.,A.oostomaPáll-Gergely & Vermeulen,sp. nov.,A.papaverPáll-Gergely & Hunyadi,sp. nov.,A.parallelaPáll-Gergely & Hunyadi,sp. nov.,A.prolixaPáll-Gergely & Hunyadi,sp. nov.,A.pusillaPáll-Gergely & Hunyadi,sp. nov.,A.pustulataPáll-Gergely & Hunyadi,sp. nov.,A.quadridensPáll-Gergely & Vermeulen,sp. nov.,A.raraPáll-Gergely & Hunyadi,sp. nov.,A.reticulataPáll-Gergely & Hunyadi,sp. nov.,A.somsakiPáll-Gergely & Hunyadi,sp. nov.,A.steffekiPáll-Gergely & Grego,sp. nov.,A.tetradonPáll-Gergely & Hunyadi,sp. nov.,A.thersitesPáll-Gergely & Vermeulen,sp. nov.,A.tonkinospiroidesPáll-Gergely & Vermeulen,sp. nov.,A.tridentataPáll-Gergely & Hunyadi,sp. nov.,A.tweedieiPáll-Gergely & Hunyadi,sp. nov.,A.uvulaPáll-Gergely & Hunyadi,sp. nov.,A.vandevenderiPáll-Gergely & Jochum,sp. nov.,A.vitrinaPáll-Gergely & Hunyadi,sp. nov.,A.vomerPáll-Gergely & Hunyadi,sp. nov.,A.werneriPáll-Gergely & Hunyadi,sp. nov.AngustopilasubelevataPáll-Gergely & Hunyadi, 2015 is moved to the synonymy ofAngustopilaelevata(F. G. Thompson & Upatham, 1997), andA.singuladentisInkhavilay & Panha, 2016 is a junior synonym ofA.fabellaPáll-Gergely & Hunyadi, 2015. Three species, namelyA.elevata,A.fabellaandA.szekeresi, are widespread over several hundred kilometres while some other species (A.huoyani,A.parallelasp. nov.,A.cavicolasp. nov.) are known from just two sites a few hundred kilometres apart. All others are small range or single-site endemics. The reproductive anatomy ofA.erawanicasp. nov.is described.