Contemporary urbanization faces interconnected challenges such as environmental degradation, socio-spatial inequalities, and the need for technological innovation. In this context, the paradigms of smart cities and sustainable cities emerge as proposals for global urban planning. While smart cities prioritize advanced technologies – such as IoT, big data, and artificial intelligence – to optimize urban efficiency, sustainable cities aim to balance economic growth, social inclusion, and environmental preservation, aligning with SDG 11 of the UN's 2030 Agenda. Despite their promises, these models face structural contradictions and often fail to overcome barriers such as digital exclusion, elitization, and centralized governance. This study aims to critically analyze the convergences and divergences between the smart cities and sustainable cities models, proposing a hybrid model that integrates technological innovation and socio-environmental justice. Methodologically, it employs the deductive method and systematic bibliographic review. The analysis is based on critical interpretation and hermeneutics of academic texts and technical documents, consolidating an updated theoretical overview of the two paradigms. The results indicate that integration between the models is not only possible but also necessary to address contemporary urban challenges. An integrated model should prioritize participatory governance, technological accessibility, and inclusive sustainable practices, overcoming the structural limitations of both paradigms. It is concluded that, by aligning technological advances with principles of social equity and environmental preservation, it will be possible to build more resilient, innovative, and well-prepared cities to face the challenges of the 21st century.