The influence of stress triaxiality and Lode parameter on microvoid growth phase of ductile fracture under ultra-low cycle fatigue (ULCF) (Nf < 100, Nf = cycles to failure) loading is investigated using micromechanical analyses. A new micromechanical cyclic void growth model (MM-CVGM) to predict the ULCF life of ASTM A992 steels is presented. The MM-CVGM is calibrated and validated from the experiments conducted on axisymmetrically notched specimens. Number of cycles to failure (Nf) and the fracture initiation locations predicted by the model closely matched the experimental observations.