This paper addresses the topic of the assessment of an organization's external environment and more particularly the lack of research providing conceptual foundations for developing suitable strategic information systems supplying managers with the necessary information and analysis tools to consider the key environmental aspects that are relevant to strategic decision making. Inspired by research in the field of domain and enterprise ontologies, this paper argues that the development of a formal model of the environment would help solve this problem. As a result, this paper develops a conceptual model of the environment that assembles the available but scattered knowledge on this topic and translates it into a more formal form that may facilitate the creation of environmental information systems and tools and demonstrates its usefulness by applying it to analyze a concrete environment.