Conodonts from the early Ordovician Horn Valley Siltstone in the Amadeus Basin, Northern Territory, Australia are described as illustrated. Samples were collected from limestone beds within the unit at two easily accessible localities. Twenty-two multielement species belonging to 17 genera are described. One new genus (Jumudontus) and eight new species (Acodus buetefueri, Drepanoistodus pitjanti, Erraticodon patu, Jumudontus gananda, Prioniodus amadeus, Protoprioniodus yapu) are proposed. The report also constitutes a revision of a small conodont collection described by Crespin (1943). The Horn Valley conodonts are mid-Arenig in age. They correlate with conodont zones OCD and OCE of McTavish and Legg (1976) in the Canning Basin, north-west Australia and relate to faunas from the Oepikodus evae and Baltoniodus triangularis/Baltoniodus navis Zones on the Baltic Platform. In North America, the Horn Valley conodonts are equivalent to late Fauna E, Fauna 1 and early Fauna 2 of the Midcontinent succession, thus indicating an uppermost Canadian and early Whiterock age.