The purpose of the research paper is to highlight the political, diplomatic, and military-technical assistance to Ukraine by the government of Great Britain led by Boris Johnson during the full-scale invasion of the Russian Federation in February - September 2022. The scientific novelty is in the fact that the role and place of the government of B. Johnson in uniting Western countries in support of Ukraine, supplying modern British weapons to the Armed Forces of Ukraine, and diplomatic support for Ukraine, both at the bilateral level and in international organizations and at international forums are holistically and comprehensively analyzed in the paper. The volumes, forms, terms, and peculiarities of providing assistance are revealed. The influence of the extraordinary personality of B. Johnson and his special attitude towards Ukraine and helping the Ukrainian people in the fight against Russian armed aggression are considered. Conclusions. The main areas of British assistance to Ukraine were outlined even before the Russian full-scale invasion. The UK, mainly due to the efforts of Prime Minister B. Johnson, was a leader in providing military-technical support (for example, NLAW, lightweight shoulder-fired, and disposable line-of-sight missile system) and training Ukrainian military specialists. In particular, political and diplomatic support consisted of active work with the United Kingdom's NATO allies and EU countries, aimed at forming a coalition to assist Ukraine and developing and implementing a joint sanctions policy against the aggressor country. With the beginning of Russian full-scale aggression, the issue of supporting Ukraine and its victory in the war became one of the priority political tasks and moral and value guidelines for B. Johnson. Along with US President Joseph Biden, he became the initiator and organizer of large-scale multi-level assistance to Ukraine at the state and international levels. It was the British government that was the first among foreign countries to provide Ukraine with various types of lethal, in particular heavy, high-tech weapons, encouraging other world leaders to do the same. At the same time, that was supplemented by training thousands of Ukrainian military men, supplying ammunition and equipment to the Armed Forces of Ukraine, and financing the repair of military equipment.