Urbanization is a major driver of land use change and global environmental decline. With accelerated urbanization worldwide, it is essential to put in place new policies to conserve urban ecosystems, species and the services these provide in order to secure more sustainable, resilient and livable cities for the 21st century. In urban planning, the concept of resilience has broadly replaced the word sustainability. In recent years, resilience indicators have been gradually developed, but few address urban resilience from a social-ecological systems perspective. We develop a methodological framework to measure urban resilience, define an urban resilience index and apply it to Spanish province capitals as a case study. Results show that most Spanish province capitals are far from being resilient. We conclude that increased efforts to measure urban resilience should be in place, and we offer the urban resilience index as a theoretical framework for measuring resilience in urban social-ecological systems that can be gradually improved as more data become available.