Reliable crowdsourcing is a distributed data collection and annotation approach that incorporates systematic quality-control mechanisms to produce accurate, high-quality ground-truth data from a diverse and potentially noisy pool of human contributors. Because individual crowd workers often exhibit varying degrees of expertise, attention, or subjective bias, this method relies on strategies such as redundant multi-worker task assignment, consensus modeling, and statistical or algorithmic filtering, such as expectation-maximization, to identify and discard unreliable annotations. By aggregating repeated inputs and mitigating noise, reliable crowdsourcing establishes consistent, high-fidelity datasets essential for training and evaluating machine learning and artificial intelligence systems.