The R package **coin** implements a unified approach to permutation tests, providing a wide range of independence tests for nominal, ordered, numeric, and censored data, as well as multivariate data. The package is based on a flexible conceptual framework that embeds different permutation test procedures into a common theory, and it establishes a computational framework that embeds the corresponding R functionality in a common S4 class structure with associated generic functions. This allows for easy implementation of conditional inference functions for various special cases, such as classical tests for location, scale, and association problems. The paper provides a detailed exposition of the internal structure of the package, user interfaces, and examples of how to extend the implemented functionality. It also includes a practical example using categorical data to illustrate the use of the software.The R package **coin** implements a unified approach to permutation tests, providing a wide range of independence tests for nominal, ordered, numeric, and censored data, as well as multivariate data. The package is based on a flexible conceptual framework that embeds different permutation test procedures into a common theory, and it establishes a computational framework that embeds the corresponding R functionality in a common S4 class structure with associated generic functions. This allows for easy implementation of conditional inference functions for various special cases, such as classical tests for location, scale, and association problems. The paper provides a detailed exposition of the internal structure of the package, user interfaces, and examples of how to extend the implemented functionality. It also includes a practical example using categorical data to illustrate the use of the software.