The Otway Basin is a Jurassic to Pliocene sedimentary basin formed on the southern Australian continental margin, and associated with rifting and breakup of the Australian and Antarctic plates. Lithospheric cooling and contraction produced post-breakup subsidence. Either lithospheric stretching or deep crustal metamorphism produced pre-breakup subsidence. Stages of hydrocarbon maturity of Otway Basin sediments can be modeled. Thermal history depends on the subsidence mechanism applied to the basin. A paleo-heat-flow history derived from the deep crustal metamorphism model of subsidence produces a maturation profile with depth that is consistent with observed vitrinite reflectance data.--Modified journal abstract.