In recent years, a noticeable contradiction has emerged between the disorderly sprawl and fragile climate environment of many cities, especially in mountainous cities. Therefore, this paper respectively constructed evaluation indicators for urban sprawl sustainability (USS) and climate change adaptability (CCA). Next, a coupling coordination degree model was used to measure the coordinated development of USS and CCA. Finally, this paper analyzed the coordinated development type of USS and CCA in the Chongqing metropolitan area from 2007 to 2017. The results of this paper show that USS and CCA have gradually shifted to coordinated development in the Chongqing metropolitan area during the study period. However, there were obvious regional differences in the type of coordinated development in the Chongqing metropolitan area. The coordinated development degree of USS and CCA in nine districts ranged from 0.635 to 0.721 in 2017. It can be divided into three types: slightly coordinated development with lagging CCA; slightly coordinated development with lagging USS; and moderately coordinated development with lagging CCA. Those districts should give priority to the use of Nature-Based Solutions (NBS), and multi-center and multi-group approaches to enhance the coordinated development between USS and CCA, which is also helpful for mountainous cities in China and other countries. decline of urban climate change adaptability. Therefore, ways to urban sprawl sustainability while adapting to climate change have become a key issue in urban sustainable development.Mountainous cities are cities that are distributed mainly in mountainous areas, hills and rugged plateaus, which have different urban morphologies and ecological environments than plains and plateau cities [10]. Constrained by their own unique geological, hydrological, land, ecological environments, and natural resources, mountain cities are characterized by high sensitivity, weak compressive capacity, and poor self-adaptability [10,11]. In specific times and spaces, compared with other types of cities, mountainous cities are more vulnerable to climate change. And as western mountainous cities are in a period of rapid urban sprawl-affecting urban populations, spaces, economies, and other aspects-the impacts of climate change are even more serious. Therefore, the coupling relationship of climate change adaptability and urban sprawl sustainability in mountainous cities has become an important aspect of current urban sustainable development research.Coupling is a concept derived from the physical relationship between two (or more) subjects [12]. For example, when two pendulums are connected to a spring, their vibrations fluctuate and interact with each other. This interaction is called pendulum coupling. From an ecosystem perspective, coupling refers to the interaction, mutual evolution, and subsequent development of two or more system elements (or subsystems) [12]. Similarly, the phenomenon of interaction and mutual evolution between urban sprawl and climate change syst...