The effect ofmaterialorientation on cyclic deformation and fatigue behavior of rolled AZ80 magnesium (Mg) alloy was experimentally investigated under fully reversed strain-controlled loading in ambient. The testing specimens were taken from a rolled AZ80 Mg plate at four orientations with respect to rolled plane: 0˚(ND, normal direction), 30˚(ND30), 60˚(ND60), and 90˚(RD, rolled direction). Fatigue fracture morphologies of specimens along differentorientation wereanalyzed by scanning electron microscopy (SEM).Overall cyclic hardening was observed for the material loaded in different directions. For a given strain amplitude, the ND specimens had the lowest fatigue resistance among the specimens of all material orientations.The fatigue lifeof an ND30 specimens is similar to that of an ND60 specimenat a given strain amplitude and both are higher than that of anRD specimenwhenthe strain amplitude is higher than 0.4%, whereasanRD specimen exhibits a better fatigue resistancewhen the strain amplitude is lower than 0.4%. A mixed fracture mode with transgranular and intergranularcracking related tolamellar-like features occurred during stablecrackgrowth, and anintergranular fracture moderelated todimple-likefeatures exhibited inthe fast fracture region. A multiaxial fatigue model based on the strain energy density can correlate all the fatigue experiments of the material at different material orientations.