Goblin spiders of the genus Ischnothyreus are characterized by small, heavily sclerotized male pedipalps, reduced dorsal and ventral scutes, and heavy spination of the first and second legs. Species of this genus may be distinguished from each other by the variation in the embolic region of the male palp, female genitalia, color, degree and shape of dorsal and ventral sclerotization, and specializations of the chelicerae and endites in the male. A total of 34 Australian species of Ischnothyreus Simon are recognized, all of which are endemic and found throughout the tropical, monsoonal, and subtropical regions of the country. Ischnothyreus darwini Edward and Harvey is the only previously described species, and 33 are newly described: I. arcus, I. barratus, I. bifidus, I. binorbis, I. boonjee, I. bualveus, I. bupariorbis, I. collingwoodi, I. comicus, I. corniculatum, I. cornuatus, I. crenulatus, I. culleni, I. digitus, I. eacham, I. eungella, I. florence, I. hamatus, I. hoplophorus, I. julianneae, I. ker, I. meidamon, I. monteithi, I. nourlangie, I. ovinus, I. piricius, I. pterodactyl, I. puruntatamerii, I. raveni, I. rixi, I. stauntoni, I. tragicus, and I. tumidus. Many of the described species have extremely small geographic ranges, and the genus shows high diversity over relatively small areas. A key, detailed illustrations, and digital images are provided for all Australian species of Ischnothyreus.