The Ibero-American Congress of Smart Cities (ICSC-CITIES), a forum for Smart Cities discussion, presents this book of articles from its sixth conference, held in presential and virtual mode format in Ciudad de México and Cuernavaca, México, from November 13-17, 2023. A Smart City is a framework composed mainly of Internet of Things systems and Information and Communication Technologies integrated to develop, implement, and promote sustainable development practices and face the challenges of urbanization. ICSC-CITIES aims to create synergies among different research groups to promote the development of Smart Cities and contribute to their knowledge and integration in different scenarios.The conference has been held yearly since 2018. The first and the second editions, i.e., 2018 and 2019, were celebrated in Soria, Spain. The third edition was celebrated virtually but hosted by the Costa Rica Institute of Technology. The fourth edition was hosted by Instituto Politécnico Nacional de México, celebrated in presential and virtual mode in Cancún, México. The fifth edition was hosted by Universidad de Cuenca and celebrated in presential and virtual mode in Cuenca, Ecuador. The VI Ibero-American Congress of Smart Cities (ICSC-CITIES 2023) was held in a hybrid way (face-to-face and virtual) from November 13th to 17th, 2023, in Ciudad de México and Cuernavaca, hosted and sponsored by the Centro de Investigación en Computación of the IPN and Universidad Autónoma del Estado de Morelos, México. Seventy-five technical presentations were given by researchers from 26 different countries during the ICSC-CITIES 2023. Eleven papers were included as posters. Papers were divided into eleven tracks, i.e., Artificial Intelligence for Smart Cities, Energy, Energy Efficiency and Sustainability, Smart grid, Governance and Citizenship, Smart Economy, Development and Education, Smart Environment, Smart Industry, Smart Mobility, Smart Public Services and Urban Informatics, Big Data, Analytics for Smart Cities & Other developments for Smart Cities; those contributions were selected from a pool of 94 submitted papers, yielding an acceptance rate of 91.4%.ICSC-CITIES 2023 was enriched by three-featured panel discussions focusing on specific aspects of Smart Cities. The first panel explored how new technologies foster the development of new smart cities. The second panel discussed the digitalization of public transportation and its benefits. The final panel examined smart cities from a gender perspective.