In this paper, the stress-strain hysteresis loops of fiber-reinforced ceramic-matrix composites (CMCs) under in-phase/out-of-phase thermomechanical and isothermal cyclic loading have been investigated. The thermomechanical hysteresis loops models have been developed considering synergistic effects of thermal temperature cycling, stress levels and fiber/matrix interface debonding. The relationships between thermal cyclic temperatures, peak stress, fiber/matrix interface shear stress and stress-strain hysteresis loops under in-phase/out-of-phase thermomechanical and isothermal cyclic loading have been established. The effects of fiber volume fraction, peak stress, matrix crack spacing, interface frictional coefficient, interface debonded energy and temperature range on the stress-strain hysteresis loops under in-phase/out-of-phase thermomechanical and isothermal cyclic loading have been analyzed. The hysteresis loops of cross-ply SiC/magnesium aluminosilicate (MAS) composite under in-phase/out-of-phase thermomechanical and isothermal fatigue loading have been predicted. [GRAPHICS] .