We present a phylogeny based on four DNA molecular markers (rps16–trnK spacer, rps16 intron, rpl32–trnL spacer and ITS) concentrating on species of Eragrostis Wolf in Australia. Two Australian radiations are shown within Eragrostis, one being centred in the arid zone and one in the monsoon tropics. The genus is paraphyletic, with species of Cladoraphis Franch., Ectrosia R.Br., Harpachne Hochst. ex A.Rich., Heterachne Benth., Neeragrostis Bush, Planichloa B.K.Simon, Psammagrostis C.A.Gardner & C.E.Hubb. and Stiburus Stapf together forming a well supported clade mixed with Eragrostis species. The molecular results are consistent with recognition of an expanded Eragrostis and we make the following new combinations for Australian taxa: Eragrostis agrostoides (Benth.) R.L.Barrett & P.M.Peterson, E. anomala (C.E.Hubb.) R.L.Barrett & P.M.Peterson, E. appressa (S.T.Blake) R.L.Barrett & P.M.Peterson, E. baileyi (C.E.Hubb.) R.L.Barrett & P.M.Peterson, E. blakei (C.E.Hubb.) R.L.Barrett & P.M.Peterson, E. confusa (C.E.Hubb.) R.L.Barrett & P.M.Peterson, E. danesii (Domin) R.L.Barrett & P.M.Peterson, E. gulliveri (F.Muell.) R.L.Barrett & P.M.Peterson, E. leporina (R.Br.) R.L.Barrett & P.M.Peterson, E. nervilemma (B.K.Simon) R.L.Barrett & P.M.Peterson, E. ovata (Night.) R.L.Barrett & P.M.Peterson, E. scabrida (C.E.Hubb.) R.L.Barrett & P.M.Peterson, E. wiseana (C.A.Gardner & C.E.Hubb.) R.L.Barrett & P.M.Peterson and Sporobolus ramigerus (F.Muell.) P.M.Peterson, Romasch. & R.L.Barrett, and propose the following new names: E. divergens R.L.Barrett & P.M.Peterson, E. lilliputiana R.L.Barrett & P.M.Peterson and E. nightingaleae R.L.Barrett & P.M.Peterson. Lectotypes are designated for Ectrosia agrostoides Benth., E. anomala C.E.Hubb., E. appressa S.T.Blake, E. baileyi C.E.Hubb., E. blakei C.E.Hubb., E. confusa C.E.Hubb., E. gulliveri F.Muell., E laxa S.T.Blake, E. leporina R.Br, E. leporina var. longiglumis C.E.Hubb., E. schultzii Benth., E. schultzii var. annua C.E.Hubb., E. spadicea R.Br., Glyceria australasica Steud., Heterachne gulliveri Benth., Heterachne gulliveri var. major C.E.Hubb. Poa ramigera F.Muell. and Psammagrostis wiseana C.A.Gardner & C.E.Hubb.