Neil Brenner’s ‘What is Critical Urban Theory?’ defines critical urban theory as more than a radical tradition within urban studies: it is a historically situated mode of critique directed against the power relations that produce capitalist urbanisation. Brenner contrasts critical urban theory with mainstream, technocratic or market-oriented urban knowledge, arguing that cities should not be treated as neutral expressions of efficiency, bureaucratic order or universal social laws. Instead, urban space is politically produced, ideologically mediated and socially contested. Drawing on Marx and the Frankfurt School, Brenner identifies four elements of critical theory: it is theoretical rather than merely practical; reflexive about its own historical conditions; opposed to instrumental reason; and committed to exposing the gap between existing reality and emancipatory possibility. This framework matters because urbanisation is no longer a secondary issue within capitalism. In the twenty-first century, Brenner argues, urbanisation has become increasingly generalised across the world, extending beyond cities into metropolitan regions, infrastructures, settlement networks and planetary landscapes. Critical urban theory must therefore analyse how capital accumulation, state power, inequality, ecological crisis and everyday life are reorganised through urban processes. Its purpose is not simply to describe cities, but to reveal how existing urban formations suppress alternative futures. The article’s central political claim is that another form of urbanisation—more democratic, just and sustainable—remains possible, even if it is blocked by dominant institutions and ideologies. Ultimately, Brenner presents critical urban theory as an indispensable tool for understanding and challenging the contemporary world, because under global capitalism the urban has become a central terrain where social domination is reproduced and where emancipatory struggles may also emerge.