Terahertz laser sources with stable power levels are requested for astronomical, communication and spectroscopic applications. Here we demonstrate the amplitude stabilization of a terahertz quantum cascade laser with a graphene loaded split-ring-resonator array. This integrated amplitude modulator operates at room temperature and is capable of actively modulating the quantum cascade laser power level and stabilizing the power output via a PID loop. The laser power fluctuation was reduced from 1.82% to 0.19% of the total power
