Urban Informality and the Built Environment reframes urban informality not as a residual defect of weak planning or state failure, but as a relational condition produced through infrastructures, exchanges, images, materials and everyday spatial practices. Its central intervention is to move beyond state-centred definitions of the informal, which too often measure urban life against formal legality, regulation or administrative visibility, and instead foreground the built environment as an active socio-political force. Informal settlements, markets, water systems, walls, streets and self-built adaptations are therefore not merely symptoms of marginalisation; they are material arrangements through which people negotiate access, visibility, livelihood, identity and collective survival. A revealing case is the discussion of infrastructure: roads, water networks, walls and public spaces do not simply connect places, but also organise power, exclusion and appropriation; when residents repurpose them, they produce alternative urban orders that may be illegible to official planning yet deeply coherent in lived practice. The book’s emphasis on infrastructure, exchange and image enables a more nuanced reading of informality as both constrained and inventive, precarious and productive, marginalised and constitutive of the city itself. In conclusion, the volume argues that to understand urban informality rigorously one must read the built environment not as background, but as a contested medium through which urban inequality, agency and possibility are materially composed.