Electronic commerce (e-commerce) is getting more and more important in people’s every day shopping routines. Vendors who want to establish an online channel besides their traditional retail practice have to integrate the two supply chains. The underlying information technology systems should be able to support the integration of the new and old processes. While reference models are a popular means in designing this type of systems, the existing reference models in the field of e-commerce only give insight into the business processes and ignore the entire enterprise architecture. In this paper we address the lack of such a comprehensive reference architecture. Based on a systematic literature review, on current trends, and best practices in ecommerce landscapes we derive a reference model for service-oriented e-commerce architectures. The proposed architecture integrates new business partners and customers into the internal processes.