SEXTANTE is a GIS library written in Java and an extensive set of geoprocessing modules. It is being developed under the auspices of the government of the Spanish autonomous region of Extremadura. The main aim of SEXTANTE is to provide a platform for the easy implementation, deployment and usage of rich geoprocessing functionality. Although it was originally designed with forest management in mind, SEXTANTE has evolved into an all-purpose solution and continues to cover new fields of application, such as ecology and archaeology. Hundreds of modules provide raster and vector data processing tools, tabular data analysis and diagrams. SEXTANTE is a stand-alone Java library that integrates seamlessly with many open source Java GIS (such as gvSIG, uDig or OpenJUMP). It provides user-friendly access to its modules via the host GIS. Further functionality can be easily unlocked by linking the system with WPS and GRASS GIS geoprocessing modules.