Hominin pelvic form differs dramatically from that of other primates by having more laterally facing iliac blades, a wider sacrum and a larger, transversely broad pelvic inlet. Acetabular orientation appears to differ as well, plausibly related to differences in load transmission during habitual bipedal posture and locomotion, which may, in turn, affect overall pelvic geometry. We compared acetabular orientation in humans, Australopithecus and extant anthropoids using two approaches. First, we measured the 3D orientation of the acetabulum on in silico models of individual hipbones aligned to the median plane by registering models to landmark coordinates that had been collected on articulated pelves. We fit a plane to the acetabular rim and measured its orientation relative to median, transverse and coronal planes. Second, we performed 3D geometric morphometric analyses of landmarks collected on whole pelves and on acetabula alone of 30 extant taxa, humans and Australopithecus. Results show the acetabulum is inclined further anteriorly and inferiorly in hominins compared to all other anthropoids. Acetabular orientation is generally equivalent among non-hominin anthropoids. Humans and Australopithecus have equivalent orientations despite differences in hip joint size, inlet breadth and iliac morphology. These data suggest that hip joint orientation is independent of these other aspects of pelvic form. Geometric morphometric analyses show that acetabular reorientation in hominins also influences the mediolateral breadth of the lower ilium. These results suggest that the orientation of the acetabulum is a key component in the suite of pelvic characteristics related to habitual bipedality in hominins.