Categorical data analysis is a field of statistical analysis devoted to the analysis of dependent variables that are categorical in nature. Development of analytic techniques for inference utilizing categorical random variables began around 1900 when Karl Pearson introduced the chi-square statistic (χ2). From this first introduction of tests of two-way contingency tables, the field has developed to include not only analyses of contingency tables but also more sophisticated analytic techniques such as the generalized linear mixed model. This entry defines categorical variables, outlines the most frequently utilized probability distributions for categorical variables, describes the most commonly used statistical analyses in the field of categorical data analysis, and discusses estimation methods for parameter estimates.