Strain-controlled low-cycle fatigue (LCF) response of Nickel-based superalloy (RR1000) at elevated temperature (6500C) has been studied. In the current study, a Unified Mechanics Theory (UMT) based model is presented and applied to predict the fatigue life of Nickel-based superalloy (RR1000). Entropy is used as a damage metric in the fatigue life prediction of material in the present study. LCF life prediction is made using this model, and error in prediction is within acceptable limits (