Introduction The incidence and impact of landslides, avalanches and associated debris flows is increasing in many parts of the world (Aleotti and Chowdhury, 1999; Dai et al., 2002; Petley et al., 2007; Remondo et al., 2008). The development of robust landslide risk reduction policies and decision-making frameworks ‘relies crucially on a better understanding and on greater sophistication, transparency and rigour in the application of science’ (Dai et al., 2002: 82). This call has been responded to and complemented by the parallel emergence, since the 1980s, of a risk-based approach to landslides within the geoscience and engineering communities. This chapter provides an overview of the types and causes of landslide hazards, current advances in landslide hazard and risk assessment, with focus on issues of uncertainty, and concludes with some related challenges and future research aims. The chapter includes consideration of snow avalanches, which share many of the same physical attributes in terms of triggering and emplacement dynamics. Section 9.2 defines landslide hazard and outlines three major areas of landslide research within the wider context of landslide risk assessment and management. Different landslide types and processes are identified and critical aspects of research into the physical mechanisms of triggering and emplacement are described. Section 9.3 considers: the assessment of landslide hazard using remote-sensing data and geographical information system (GIS) software; methods for assessing landslide consequences; and issues relating to data acquisition and the handling of uncertainty. Section 9.4 describes landslide risk management, providing examples of regional landslide risk assessment and decision-support systems, and selected new research developments. Section 9.5 identifies current research challenges and opportunities to advance the science.