This paper presents a fatigue life calculation for the pole, the rotor rim, and the rotor spoke of a 100 MW hydro-generator. Mechanical and electrical parameters during unit start, with the hydro-generator working at several power levels, and during a load rejection from 100 MW were measured. The measured loads together with centrifugal force, gravity, and magnetic pulling force were included in finite element models to quantify stresses. Also, stresses produced during over-speed, phase-to-ground failure, and phase-to-phase failure were evaluated. A stress history for each element was obtained by fitting the calculated stresses, with the power generation history collected hourly during one year of operation of the machine. Fatigue life calculation was performed by using the stress history along with the Wang-Brown multiaxial fatigue model.