A library for running the Wolff algorithm on arbitrary systems in arbitrary fields. A "spin state" and "spin symmetry transformation" type must be supplied to define a system, along with a spin-spin coupling, a spin-field coupling, and a generator of transformations of rank two. The library then supplies the tools to run Wolff cluster-flip Monte Carlo on the resulting system, with arbitrary measurements taken along the way. See INSTALL for installation details. Documentation is present in doc/ and can be built using Sphinx into a variety of formats. The current version of this documentation can also be found at https://doc.kent-dobias.com/wolff.