Conventional semiconductor laser emission relies on stimulated emission of photons1, 2, which sets stringent requirements on the minimum amount of energy necessary for its operation3, 4. In comparison, exciton–polaritons in strongly coupled quantum well microcavities5 can undergo stimulated scattering that promises more energy-efficient generation of coherent light by ‘polariton lasers’3, 6. Polariton laser operation has been demonstrated in optically pumped semiconductor microcavities at temperatures up to room temperature7, 8, 9, 10, 11, 12, and such lasers can outperform their weak-coupling counterparts in that they have a lower threshold density12, 13. Even though polariton diodes have been realized14, 15, 16, electrically pumped polariton laser operation, which is essential for practical applications, has not been achieved until now. Here we present an electrically pumped polariton laser based on a microcavity containing multiple quantum wells. To prove polariton laser emission unambiguously, we apply a magnetic field and probe the hybrid light–matter nature of the polaritons. Our results represent an important step towards the practical implementation of polaritonic light sources and electrically injected condensates, and can be extended to room-temperature operation using wide-bandgap materials.