Informal markets—encompassing unregistered enterprises, cash-based micro-retailing, open-air bazaars, and community distribution networks—remain the primary interface between producers and consumers in many emerging and low-income contexts. For global brands, the informal economy is not a marginal “last mile”; it is often the first mile of mass penetration, brand meaning formation, and repeat purchase. The informal economy comprises a large share of global work and enterprise activity, shaping consumer access, affordability, trust, and product authenticity in ways that standard modern retail playbooks cannot fully address. (International Labour Organization) This article develops an integrated framework explaining how global brands penetrate informal markets through (1) route-to-market architecture, (2) affordability and packaging innovation, (3) trust intermediation and social capital, (4) hybrid governance and compliance design, and (5) anti-counterfeit capability building. We synthesize multi-disciplinary literature and propose testable propositions linking informal-channel intensity to penetration outcomes (trial, availability, conversion, loyalty) under varying institutional constraints. We also outline an ethical “do-no-harm” approach to informal distribution that protects livelihoods while improving product safety, consumer rights, and resilience. Managerial implications include designing micro-distribution, leveraging micro-entrepreneurs as brand intermediaries, building data-light demand sensing, and integrating trade marketing with community-level incentives.