About 45 R packages to analyze data using item response theory (IRT) have been developed over the last decade. This article introduces these 45 R packages with their descriptions and features. It also describes possible advanced IRT models using R packages, as well as dichotomous and polytomous IRT models, and R packages that contain applications such as differential item functioning and equating are also introduced. Thus, this article helps researchers who plan to use IRT-based analysis to decide on the type of IRT analysis and choose the appropriate R packages.