The term liquid waste refers to any type of undesirable product in liquid form; it broadly describes any type of waste in liquid form including gas that has been converted to liquid form for easier handling. Common types of liquid waste include human and animal feces, household waste water, fats, cooking oils and grease as well as waste liquids produced as part of industrial processes.

Liquid waste management refers to the process of properly disposing of these wastes which often involves legal requirements about how to do so safely and so that the environment is not impacted. This is because when liquid waste is disposed of improperly, by dumping it on soil or down storm drains for example, it can potentially contaminate groundwater reserves and have significant negative health impacts. Management of liquid waste involves safely dealing with this waste so that there is no negative impact on humans or the environment.