The article is devoted to the study of the evolution of the UK's foreign policy in the period after its withdrawal from the European Union (post-Brexit period) in the context of the country's participation in the formation of the AUKUS (an abbreviation of the English names of Australia, the United Kingdom and the United States). The research methodology was formed by the principles of historicism, systematicity, and objectivity, general scientific methods of logic, comparative analysis, special historical methods of historiographic analysis, historical-systemic, chronological, historical-genetic, retrospective analysis, and comparative-historical methods of scientific knowledge. It is noted that the creation of the interstate association AUKUS in 2021 was a resonant event in the world of international politics. The agreements provide for the development of systemic military-political cooperation between the three states at the strategic level in the long term with the primacy of the US-British alliance, which will potentially have a significant impact on the configuration of the international security system, especially in the context of current attempts to revise it It is stated that the relatively recently launched international security project AUKUS has already become one of the examples of active foreign policy activities of the British governments in the post-Brexit period, which is fully consistent with the Global Britain strategy. By participating in AUKUS, the British side not only contributes to global security and strengthens its military presence in one of the key regions of world politics, protects its own geopolitical and economic interests, but also guarantees the development of high-tech knowledge-intensive industries for the long term. The project of comprehensive sectoral military and defence cooperation proposed by the United States (with the support of two allied states) reflects an attempt to maintain American and British influence in the Indo-Pacific region and globally in the face of the growing conflict with China. With the resumption of the US policy of isolationism and protectionism, and possible financial problems of the UK as the second most important partner, the AUKUS project faces uncertain prospects. Ukraine's international prospects also depend on the success or failure of the AUKUS project.