The Tertiary anatid fossils (Aves: Anatidae) from Oligocene and Miocene deposits in Australia are described. Most fossils derive from the Late Oligocene - Early Miocene (26-24 Mya) Etadunna and Namba Formations, respectively, in the Lake Eyre and Lake Frome Basins of South Australia. The local faunas from these two formations contain the same suite of anatid species. Two new genera, the oxyurine Pinpanetta, with three new species (Pi. tedfordi, 18 specimens; Pi. vickersrichae, 15 specimens; Pi. fromensis, 20 specimens), and the tadornine Australotadorna, for a large new species known from eight specimens, are established. Three anatid bones from the Waite Formation (c. 8 Mya) at Alcoota, Northern Territory reveal the presence of a tadornine that is neither Australotadorna nor an extant Tadorna species, and an indeterminate duck about the size of Malacorhynchus. Phylogenetic analyses establish Pinpanetta as a basal member of an oxyurine (stiff-tailed duck) radiation. Oxyurines are found to include the Recent Stictonetta and Malacorhynchus as basal members, along with the fossil taxa Mionetta, Manuherikia, and Dunstanetta, and the traditionally included Recent Oxyura, Biziura, Thalassornis, and Nomonyx.