Cognitive biases are systematic patterns of deviation from rationality in judgment and decision-making. First popularized by Kahneman and Tversky in the 1970s, these mental shortcuts (heuristics) help our brains process information efficiently but often lead to predictable errors. Understanding these biases is critical for anyone making consequential decisions—from business leaders and investors to healthcare professionals and everyday problem-solvers. The key insight: we are all susceptible to these biases, often without awareness, and recognizing them is the first step toward better judgment. This cheat sheet catalogs over 40 major biases, organized from foundational information-processing distortions through social dynamics, with practical debiasing strategies to help you make clearer, more rational choices.