In the 21st century, institutional investors play a crucial role in the allocation of capital in global capital markets, a significant share of which belongs to the "Big Three" investment management companies: Blackrock, Vanguard, and State Street Global Advisors. Given that the steady and prolonged growth of their presence in the markets is likely to continue, the issue of identifying the essence of such investment management companies in comparison with other investment companies requires a more thorough analysis. The author identifies three types of scientific research on the issues of investment companies and investment management companies. It is determined that the problems of their functioning are approached either via high-level generalizations or at the fragmentary level. Therefore, certain aspects of identifying the essence of investment management companies and their role in international relations require a more thorough analysis. The purpose of the article is to identify the essence of these major investment management companies and their differences in comparison with other types of investment companies. The study is based on a combination of dialectical principles of science with general scientific and special research methods in accordance with the logic of work, induction and deduction, abstraction and analogies, expert opinions and factor analysis. In order to understand the importance of studying investment management companies and their impact on the global economy, the author identifies the essence of the main types of investment funds (investment fund, exchange-traded fund, real estate investment trust, etc.). The author provides a general definition of investment management companies through activity that involves the use of collective investment for the purpose of managing index funds. Moreover, the proliferation of such companies is primarily due to the low costs of institutional asset management. Given the growing importance of non-bank financial intermediation over the past decade, the author shows that further research into the mechanism of functioning of investment management companies is important for regulating the monetary and financial stability of the world economy.