Informal development is examined as one of the key urban challenges of the present, affecting countries of both the Global North and South. The paper presents a comparative analysis of the impact of informal settlements on urban development. The study refines the conceptual boundaries of "informal settlements", proposes a typology by legal status, material-technical characteristics, and functional purpose, and identifies clusters of social, economic, political, and infrastructural-environmental risks. The dependence of the scale and configuration of the phenomenon on institutional quality, property-rights regimes, and housing affordability is demonstrated. The Russian context is considered alongside potential policy options: phased legalization, integration into utility networks, development of affordable housing, and the use of mediation mechanisms to resolve land disputes. The practical significance lies in shaping adaptive urban governance strategies aimed at reducing marginalization and enhancing territorial resilience.
