Abstract An optomechanical scheme is reported to implement single devices combining an electromagnetic resonator with a strongly nonlinear nanomechanical oscillator in order to realize light‐controlled logic functions. In this scheme, the nonlinear mechanical oscillations, which can be well controlled by external drives, are revealed to be sensitive to incident light due to light–matter interactions enhanced by the resonator. As a result, one can adjust the initial mechanical configurations to obtain various on‐demand responses to input optical signals, and thus realize reconfigurable logic functions (NOT, XOR, OR, AND). The single optomechanical device reported here is designed to work at the terahertz (THz) frequency domain, which is the first demonstration of a THz‐compatible logic component that processes information encoded in modulated free‐space THz light, with operation rates reaching a few kilohertz. This device also can be integrated into other micro‐electromechanical systems as THz‐compatible actuators. Moreover, the optomechanical scheme proposed in this work is applicable to other frequency ranges, such as radio frequencies (RF) or the infrared.