The vision of the Semantic Web is to transform the World Wide Web from a web of linked documents to a web of linked data. Using the RESTful style, Web applications can navigate among resources, discover new resources, modify them and perform other tasks. If we view an ontology as a set of triples forming a graph, it is similar in its organization to the World Wide Web. Hence, using a set of RESTful style services, we should be able to perform similar operations on an ontology. In this thesis, we present a design and a prototype implementation of RIO, a RESTful Interface to Ontologies. RIO provides a RESTful interface to manage, edit, and query OWL ontologies. RIO also provides a novel way of navigation within an ontology based on URIs representing ontology paths. In addition, RIO provides a unique way to execute SPARQL queries in a RESTful way.