We describe 22 new species in the genusHyphantrophagaTownsend, 1892 (Diptera: Tachinidae) from Area de Conservación Guanacaste (ACG) in north-western Costa Rica. All species were reared from an ongoing inventory of wild-caught caterpillars spanning a variety of families (Lepidoptera: Bombycidae, Crambidae, Depressariidae, Doidae, Erebidae, Euteliidae, Gelechiidae, Geometridae, Hedylidae, Hesperiidae, Immidae, Lasiocampidae, Limacodidae, Megalopygidae, Mimaloniidae, Noctuidae, Nolidae, Notodontidae, Nymphalidae, Papilionidae, Pieridae, Phiditiidae, Pterophoridae, Pyralidae, Riodinidae, Saturniidae, Sphingidae, Thyrididae, Tortricidae and Zygaenidae). We provide a morphological description of each species together with information on life history, molecular data and photographic documentation. In addition to the new species, we provide a redescription of the genus, as well as the redescription of three previously described species, which were also collected within ACG during this study:Hyphantrophagaangustata(van der Wulp),Hyphantrophagamyersi(Aldrich) andHyphantrophagavirilis(Aldrich & Webber).The following 22 new species ofHyphantrophagaare described:HyphantrophagaadrianguadamuziFleming & Woodsp. n.,HyphantrophagaalbopilosaFleming & Woodsp. n.,HyphantrophagaanacordobaeFleming & Woodsp. n.,HyphantrophagacalixtomoragaiFleming & Woodsp. n.,HyphantrophagacalvaFleming & Woodsp. n..,HyphantrophagaciriloumanaiFleming & Woodsp. n.,HyphantrophagadanausophagaFleming & Woodsp. n.,HyphantrophagadiniamartinezaeFleming & Woodsp. n.,HyphantrophagaduniagarciaeFleming & Woodsp. n.,HyphantrophagaedwinapuiFleming & Woodsp. n.,HyphantrophagaeldaarayaeFleming & Woodsp. n.,HyphantrophagaeliethcantillanoeFleming & Woodsp. n.,HyphantrophagagilberthampieiFleming & Woodsp. n.,HyphantrophagaguillermopereiraiFleming & Woodsp. n.,HyphantrophagahazelcambroneroaeFleming & Woodsp. n.,HyphantrophagaluciariosaeFleming & Woodsp. n.,HyphantrophagamanuelriosiFleming & Woodsp. n.,HyphantrophagamorphophagaFleming & Woodsp. n.,HyphantrophaganigricaudaFleming & Woodsp. n.,HyphantrophagaosvaldoespinozaiFleming & Woodsp. n.,HyphantrophagapabloumanaiFleming & Woodsp. n.andHyphantrophagasimilisFleming & Woodsp. n.The following are proposed by Wood as new synonyms ofHyphantrophagaTownsend, 1892:BrachymasiceraTownsend, 1911syn. n.,OmmasiceraTownsend, 1911syn. n.,OphirosturmiaTownsend, 1911syn. n.,PatillaliaCurran, 1934syn. n.andYpophaemyiopsTownsend, 1935syn. n.The following nine new combinations are proposed as a result of the new synonymies:Hyphantrophagaadamsoni(Thompson, 1963),comb. n.,Hyphantrophagafasciata(Curran, 1934),comb. n.,Hyphantrophagaglauca(Giglio-Tos, 1893),comb. n.,Hyphantrophagagowdeyi(Curran, 1926),comb. n.,Hyphantrophagamyersi(Aldrich, 1933),comb. n.,Hyphantrophaganigripes(Townsend, 1928),comb. n.,Hyphantrophagaoptica(Schiner, 1868),comb. n.,Hyphantrophagapolita(Townsend, 1911),comb. n.,Hyphantrophagasubpolita(Townsend, 1912),comb. n.