The article substantiates the conceptual principles of reducing food loss and food waste from the standpoint of ensuring food security and environmental sustainability. The approaches to the interpretation of the concepts of food loss and waste are summarized, the similarities and differences between them, as well as the reasons for their formation and the connection between them, are noted. The main causes of food losses and food waste, which are caused by human, technical-technological, natural-climatic, economic, market, etc., are considered. factors. It is argued that Ukraine's waging of war caused the deterioration of food security both at the local and national levels, and at the international level. The main factors that lead to the loss of agri-food in the supply chain during wartime and the decrease in its production volumes are systematized, which will negatively affect the provision of food security in the country and the formation of export potential at the level of previous years. The dynamics of losses in terms of individual types of products were analyzed and it was established that the highest losses are observed for potatoes - 18.1 %, vegetables and melons - 12.0 %, fruits and vegetables - 10.0 %, and for livestock products this indicator is not significant It was found that the greatest losses of crop products occur at the stage of growing and harvesting, the value of which varies from 3 to 12 %, as well as sales. In dairy and meat breeding, the greatest losses occur at the stage of livestock breeding, milking and primary processing of products, as well as due to the lack of a full production cycle. It is estimated that the amount of food waste in Ukraine in households is 76 kg per capita, which is almost equal to the indicators of most countries, but the values are higher in the catering sector - 28 kg and retail trade - 16 kg. It was concluded that there is a need to develop effective measures to reduce food waste and losses in order to increase the sustainability and competitiveness of agri-food supply chains. It is substantiated that the conceptual principles of the need to reduce food losses and food waste should be considered in the aspect of ensuring food security and minimizing the negative impact on the environment. Among the priority directions for solving the problem of food losses and waste, the following are highlighted: development of a comprehensive program for the preservation and restoration of agricultural production in the conditions of martial law; development and improvement of market infrastructure elements; technical and technological modernization of agricultural production, processing facilities; improvement of distribution infrastructure elements, especially transportation of live animals; creation of innovative warehouse facilities; formation of a rational consumption culture among the population; development of wholesale food markets, livestock markets, development of public-private partnerships in the implementation of projects to reduce food losses and food waste; development of effective levers of state regulation in the aspect of motivation of chain participants; development of a methodical approach to estimating the amount of food losses; formation of an information array of data, etc. Key words: food loss, food waste, supply chain, food security, environmental sustainability, martial law.