Many-body localization (MBL) is a phase of quantum matter that has attracted much experimental and theoretical attention recently. MBL particles stay fixed for long times, resisting thermalization. This athermality, the authors show, can serve as a resource in thermodynamic tasks. They formulate an engine cycle for a quantum many-body system tuned between MBL and thermal phases. MBL enables the engine to scale robustly, from mesoscale to macroscale, and improves the engine’s reliability. This work opens the door to technological applications of MBL.