SySTEM 2020 is a multi-faceted project focused on evaluating the impact and delivery of science learning outside of the classroom. The intention of the project is to map current informal and non-formal learning organisations and activities across Europe, evaluate a number of existing programmes, and use this information to design a robust framework for informal science education. The purpose of this paper is to conduct a systematic literature review of recent publications exploring and creating informal and non-formal science learning frameworks, to categorise these, identify gaps in the field, and to propose a consolidated framework which will provide the basis for future work. The paper will also consolidate the viewpoints of our analysed literature and create a consensus definition for formal, non-formal, and informal learning to be used as a reference for future work.