SWIP is a Semantic Web IoT Platform for Large-Scale Deployment of Heterogeneous Systems. SWIP leverages Sensing-as-a-Service as a tool for deploying IoT systems at large. SWIP is based on a proposed ontological structure that ensures unified data representation. This ontological structure, includes all aspects related to heterogeneous IoT system, including hardware, software, and applications. In addition, a set of APIs are proposed to manage the database (insertion, deletion, modification, querying, etc.). In order to allow non-tech savvy users to add sensors to this system, a user-friendly web interface is designed. This web interface also acts as a visualization tool for the proposed ontology. Furthermore, SWIP considers the fact that IoT systems are rapidly evolving, which means that the backend ontological structure should be adaptable as well. Thus, the web interface incorporates tools that allow users to modify the ontology. A set of consistency checks are proposed to ensure stable operation. Moreover, SWIP allows administrators to generate images of the ontological structure so that they can create system domains. Accordingly, SWIP allows data reuse across different hardware platforms without compromising administrative control. The proposed platform has been thoroughly evaluated through a real cloud deployment and the results demonstrate efficient performance.