Based on rapidly changing market conditions and increasing pressure on cost and productivity, companies in different industries have started to concentrate on their core competencies and to decrease vertical range of manufacture. This resulted in an increasing dependency between the producing companies and their suppliers. Enterprise networks are formed emerging the necessity to focus on the strategic development of supply network partners. While currently strategic purchasing mainly deals with direct suppliers future strategic purchasing needs to deal with flexible and dynamic supply networks. This results in a paradigm shift in the domain of strategic sourcing from a supplier centric to a supply network scope. In order to support the paradigm shift the development of a reference model specifying the organizational and functional implications is necessary. This chapter therefore introduces a reference model for the domain of strategic supply network development extending the traditional frame of reference in strategic sourcing to a supply network perspective.