Landfills can be regarded as a particular type of contaminated land that has a potential to directly and indirectly pollute all of the four main spheres of the environment which are the lithosphere, atmosphere, hydrosphere and eventually adversely impact the biosphere. Therefore, environmental risk assessment of a landfill has to be more integrated and holistic by virtue of its nature of being a multidimensional pollutant source. Despite this, although various risk assessment approaches have been adopted for landfill waste disposal sites, there are still wide-ranging knowledge gaps and limitations which need to be addressed. One important knowledge gap and limitation of current risk assessment approaches is the inability to fully identify, categorise and aggregate all individual risks from all combinations of hazards, pathways and targets/receptors (e.g. water, air, soil and biota) in connection to a certain landfill leachate and yet at any stage of the landfill cycle. So such an approach is required that could not only integrate all possible characteristics of varying scenarios but also contain the ability to establish an overall risk picture, irrespective of the lifecycle stage of the landfill (e.g. planning stage/pre-operation, in-operation or post-operation/closed). One such approach to address the wide-breadth of landfill impact risks is by developing a more holistic risk assessment methodology, whose conceptual framework is presented in this paper for landfill leachate in a whole-system format. This conceptual framework does not only draw together various constituting factors and sub-factors of risk assessment in a logical sequence and categorical order, but also indicates the “what, why, when and how” outputs of and inputs to these factors and sub-factors can be useful. The framework is designed to identify and quantify a range of risks associated with all stages of the landfill lifecycle, and yet in a more streamlined, logical, categorical and integrated format, offering a more standardised and unified whole-system approach.