It would seem that humanity received two doses of the vaccine in the 20th century to reject the desire to wage aggressive war forever. However, the beginning of the 21st century was also marked by the war of aggression that Russia started against Ukraine. The territory of Ukraine suffered (and continues to suffer) special losses: it was the theater of hostilities of the First World War, the Second World War, and now another war is destroying life, the country, and our cultural heritage. War, like any other type of destructive activity, negatively affects people's lives, the economy of countries, and the world in general; the sphere of culture suffers, including museums. At this stage, it is possible conditionally distinguish two periods in the Russian-Ukrainian war (respectively, two stages in the activity of museums at this time): 1) February 2014 - February 24, 2022; 2) after February 24, 2022. Russia's aggression against Ukraine began in February 2014 with the occupation of Crimea, the organization of pro-Russian rallies in cities in the east and south of Ukraine, and the occupation of certain areas of Luhansk and Donetsk regions. Museum institutions in these territories became automatically under occupation or under threat of destruction as a result of hostilities. The central government of Ukraine was not ready for aggression and occupation, museum collections were not evacuated, even information about these collections can be considered lost. According to the registers of the Ministry of Culture and Information Policy, by 2014 there were 99 museums in Crimea, 24 in Donetsk Oblast, 23 in Luhansk, which stored hundreds of thousands (perhaps millions) of movable cultural heritage items. After February 24, 2022, the entire heritage of Ukraine, both cultural and natural, is under threat of destruction, because Russian missiles can reach any point in Ukraine (and not only). Museums in the territory controlled by Ukraine or evacuated from the occupied territory must resume their activities. For the evacuated institutions, the problem of restoring the statutory and financial documentation and the museum staff actually arose. Other museum institutions have started the process of documenting the course of military actions in Ukraine and informing the world about the events in Ukraine. Museum institutions and individual employees are coming together to help each other in difficult times: the Heritage Rescue Headquarters and the Museum Crisis Center have been created, and initiatives that existed before the full-scale invasion continue to help museums (to cope with new challenges). Despite the disassembled exhibits, museum life in Ukraine has not stopped - new exhibitions, other cultural events, exhibitions of museum objects from Ukraine abroad are taking place, trainings and courses are organized on how to work in a crisis period, and foreign colleagues come to familiarize themselves with the experience of museums during war. Key words: museums of Ukraine, russian-Ukrainian war, museum collections, evacuation, cultural values.