There are 1474 fish species now known from the Northern Territory, in 195 families, with a number of these species still undescribed. The 1474 species include 120 new records for the NT and three for Australia, while nine non-native species exist as small feral populations.The most speciose family is the Gobiidae (gobies), with 150 recognised species, and is the main fish group inhabiting coral reef and mangrove areas. The fish fauna of the Northern Territory occupies several biogeographical regions, which include the internal river drainages of Australia and the Sahul Shelf adjoining New Guinea and Indonesia. The Northern Territory's fish fauna most closely resembles that of north-western Western Australia, and many species are shared with this region. Among the Northern Territory's fish fauna are 55 species considered to be threatened under various listings (ASFB, EPBC), with the poor state of knowledge of the NT's fish populations and their true distributions hindering assessment. Many sampling gaps remain and the basic biology of most species is unknown.