The Integrated Land and Water Information System (ILWIS, http://52north.org/communities/ilwis/) is a GIS and remote sensing software integrating raster, vector and thematic data set processing into a desktop application. ILWIS is hosted under the umbrella of the 52North project and managed and maintained by ITC, University of Twente, The Netherlands. ILWIS is currently subject to a significant refactoring and modularization process referred to as ILWIS Next Generation (ILWIS NG). This will increase attractiveness for developers and lowers their entry requirements. It will provide a sustainable code base for the next decade and allows for integration with other open source software. Beneficiaries are researchers, educators and project executers. It will allow them to use GIS and remote sensing functionality in an easy and interoperable manner on a single desktop and in a web and/or mobile environment in order to integrate their work with others in a standardized way. Based on requirements analysis meetings with a small team at ITC, an architecture was created to host the modular components of ILWIS NG. The implementation of this architecture was started in 2013 and comprised the creation of the QT-based core software centered around a plug-in concept which supports connectors. This supports different data formats and interfaces to other software packages. As first extensions, a Python API and WFS have been developed and data connectors to PostgreSQL and OGC's SWE are underway, as well as a flexible mobile app environment, making it possible to configure lightweight GIS apps within a very short time. The presentation will embark upon the justification of starting the software refactoring and will provide an overview of the new modular architecture, giving insight into the design choices which were made. The presentation will also expose the GIS and image processing functionalities within ILWIS and how they are made available in the new interoperable setup indicating the libraries and standards on which they are based. Examples will be given on the many projects in which ITC has used ILWIS already and the potential use of ILWIS Next Generation in combination with OSGEO projects in the future.