The proposed article is aimed at identifying the essence, history of development and evaluation of the current stage of regionalism. The principles of the theory of economic integration are briefly outlined, including its forms and their practical implementation. The author discusses the regulation of integration agreements within the framework of the GATT - WTO multilateral trade system. The motives for the participation of states in integration agreements, such as strategic, political and economic ones, as well as participation of the country in global and / or regional value of chains, are examined in detail. The author characterizes the main trends of modern regionalism and well-known integration mega-projects, such as the Trans-Pacific Partnership, and the Regional Comprehensive Economic Partnership. The main results of the study, which the author came to: 1) regionalism is a politics, and regionalization is the process of uniting countries into a larger region with elements of the free movement of certain factors; 2) old regionalism reflected the goals of promoting the growth of international trade and ensuring security. It corresponds to the concept of “shadow” integration; 3) the new regionalism was the result of an integrated approach to the development of globalization and a multipolar world. It is characterized by the concept of “deep” integration with deeper integration processes; 4) when signing the RTAs, the country takes into account strategic, political and economic factors; 5) integration agreements vary in scope and structure, reflecting the growing differentiation of the global trading system and the diversity of bilateral and multilateral regional trade agreements; 6) the signing of mega-projects reduces the effect of “spaghetti bowl” due to a decrease in the number of bilateral integration agreements between countries and the development of general rules of trade, and also simplifies international commercial disputes; there is a gradual unification of not only the rules of law, but also their interpretation and application.