These guidelines seek to develop a consensual, harmonized, science-based approach to the use of water in livestock production, including the assessment of water flows. Given growing competition between users, sectors and uses, it is vital to understand the distribution of, and demands for, fresh water in livestock production. Water usage for this sector should be considered an integral part of agricultural water resource management, taking into account the type of production system (e.g. grassland-based, mixed crop/livestock or landless) and scale (intensive or extensive), livestock species and breeds, and social and cultural aspects of livestock farming in different countries. The guidelines propose scientific, yet practical, approaches that build on existing or developing methodologies. They also help identify areas where ambiguity or differences exist concerning the methodological framework.The publication is a product of the Livestock Environmental Assessment and Performance Partnership, a multi-stakeholder initiative whose goal is to improve the environmental sustainability of livestock supply chains through better methods, metrics and data. It is expected to benefit organizations, governments, consumers, farmers, companies, investors and other interested parties worldwide by providing transparency, consistency, reproducibility and credibility for assessing and reporting the water demand for livestock products.