This paper presents an ontology to model the field of Information Architecture for Web (Web IA), according to the precepts defined by Morville and Rosenfeld in the book Information Architecture for the World Wide Web, version 2006. It aims to structure the related knowledge in the field of IA for the Web, formalizing this area and helping to teach the concepts and relationships in the domain of the IA for the Web. The research is theoretical and qualitative, and is classified as descriptive and exploratory. The modeling was performed using the language of Ontology Web Language (OWL) and the Protégé framework 3.4.1, by following the steps of the methodology 101. The results show the InfoArch, an ontology that represents concepts and relationships, and enables finding answers to questions about the area. It is considered that InfoArch brings contributions especially on issues of teaching, research and extension, and thus will serve as a source of information for researchers, teachers and staff of developing sites that work with Information Architecture for the World Wide Web.