Over the past century, the appraisal of nutrient-rich agricultural by-products has become imperative in addressing global-scale challenges, such as hunger, poverty and increasing population worldwide. Besides, escalating global energy consumption, climate change, environmental and economic concerns have emphasised the necessity of sustainable practices and waste management in the agri-food industry. Considering these requirements, aquafaba, a by-product of the cooking process of legumes, especially chickpeas, is often regarded as a liquid waste stream, hence, adding value to it can be an alternative to revalorise legume waste and thus contribute to the circular economy. Legumes are among the most widely consumed foods worldwide. During pulse cooking, the migration of nutrients such as polysaccharides and proteins, along with other minor components such as saponins and phenolics, into the cooking water during heat and pressure treatments makes aquafaba a valuable industrial by-product to be revalorised due to their enhanced techno-functional properties. Furthermore, it can be used directly in a new process without requiring additional treatment, highlighting its cost-effectiveness as an ingredient. Aquafaba has already started to be used in vegan/vegetarian diets as an alternative to animal-based ingredients such as egg white and whey protein, due to its well-known techno-functional properties. In recent studies, the emulsifying, foaming and thickening properties of aquafaba have been exploited on vegan cakes, cookies, meringues, and mayonnaise products, and its industrial adoption has been gaining attraction. This chapter aims to provide an updated overview of the aquafaba sources, its colloidal properties and factors affecting these properties, its current stage of development in the agri-food industry and future perspectives regarding aquafaba in the development of ‘vegan/vegetarian’ and ‘clean-label’ food formulations.