The objectives of this paper are to review journal articles published between 2003 and 2015 related to supply chain risk sources, with a view to list and define supply chain risk sources identified by various researchers and critique the various supply chain risk classification schemes. For the purpose of this literature review, we adopted the methodology of a content analysis based literature review. Towards this end a conceptual risk classification framework was defined and supply chain risks identified by various researchers mapped into it. An analysis of the surveyed literature revealed the various supply chain risk sources and associated risks identified by the researchers. It is seen that while supply chain risk classification has been done by several researchers, it is not the main focus area of research for a majority of researchers but appears supplementary to other research goals. While the various supply chain risk classification schemes reviewed have sufficient breadth or depth to effectively address the diverse variety of supply chain risks, some important risk sources like product characteristics and returns processing have scope for further research. A new, comprehensive conceptual risk classification framework has been defined for the literature review. The review takes into account the current thinking on concept of risk and supply chain risks.