We present a procedure to accelerate the relaxation of an open quantum system towards its equilibrium state. The control protocol, termed the shortcut to equilibration, is obtained by reverse-engineering the nonadiabatic master equation. This is a nonunitary control task aimed at rapidly changing the entropy of the system. Such a protocol serves as a shortcut to an abrupt change in the Hamiltonian, i.e., a quench. As an example, we study the thermalization of a particle in a harmonic well. We observe that for short protocols the accuracy improves by 3 orders of magnitude.