The article is devoted to highlighting the process of formation and development of the prerequisites for the creation of a modern set of norms of international law, aimed at protecting vulnerable groups of the population - parts of society with different numbers, with an increased risk compared to other groups or the rest of society of being affected by the effects of a discriminatory nature, becoming victims of violence (especially during armed conflicts), natural, man-made disasters or economic shocks. Usually, the term “vulnerable groups” is used for the elderly, children, certain categories of women, refugees, people with disabilities, migrant workers, indigenous peoples and national minorities, religious minorities. The chronological boundaries of the study cover the period from ancient times to 1919.Today, despite the apparent legal protection, these population groups in their everyday life still continue to face manifestations of discrimination and social stigmatization, despite the fact that international law emphasizes the principle of respect for human rights and declares the equality of people in their rights (political, economic, environmental, etc.), regardless of certain specific factors, including the nature or degree of their vulnerability.This problem became particularly acute with the beginning of the Russian-Ukrainian war. Such exceptional actualization is due to the fact that in wartime, unfavorable external and internal factors (primarily humanitarian, economic, ecological) that affect the risks of various most vulnerable categories of people falling into difficult life circumstances, compared to peacetime, are extremely intensified.The article emphasizes that in relation to the era of pre-classical international law, there is no reason to speak of any systematic protection of vulnerable categories of the population. At that time, we see only individual manifestations of a compassionate attitude towards women, children, the disabled, and the elderly. There were no special international legal acts in this area.It was noted that the actual formation of the foundations of international legal protection of vulnerable population groups took place only in the era of classical international law, especially in the second half of the 19th - at the beginning of the 20th century. An important place in the protection of vulnerable categories of the population at the end of the 19th century. signed agreements that specifically laid the international legal foundations for the protection of women, primarily the fight against trafficking in women. During this period, a number of international treaties aimed at protecting the poorest sections of the population were concluded. Among them are agreements on mutual support of poor sailors, sick people, abandoned children, etc. At the same time, important steps were taken to ensure the protection of the rights of religious minorities. An important milestone on the way to the creation of an international legal basis for the protection of vulnerable sections of the population during wartime was the adoption of the Geneva Convention on the Amelioration of the Fate of Wounded and Sick Soldiers in Land War on August 22, 1864, the Brussels Declaration on the Laws and Customs of War of 1874, the Hague the Convention on the Laws and Customs of the Land War of 1907, which, although not directly aimed at protecting the rights of vulnerable groups of the population, were nevertheless tentatively aimed at the implementation of this task.