Quantum error mitigation is a methodological approach encompassing a suite of techniques designed to reduce the impact of noise and errors on the outcomes of quantum computations performed on non-ideal hardware. This research area investigates strategies that, unlike fault-tolerant error correction, do not prevent or correct errors during computation but instead aim to estimate and subtract the effects of noise, often through calibration, clever circuit design, and post-processing of measurement data. Its key significance lies in enabling more accurate execution and analysis of quantum algorithms on Near-Intermediate Scale Quantum (NISQ) devices, thereby expanding the capabilities of current quantum systems and serving as a bridge towards future fault-tolerant computing.