Wilderness is the largely undisturbed natural area that is rarely affected by anthropogenic activities. In fact, fragments of wildness can also be found within urban areas where human disturbances are extremely low. Urban wildness refers to the urban and peri-urban spaces where the ecosystem is dominated by natural processes. Compared to the urban green infrastructure (e.g. parks, water features and blue-green networks, etc.), the species composition, structure and ecological flows, as well as ecosystem services of urban wildness are basically undisturbed by human activities, so that it has highly self-organized ecological processes, and therefore may provides greater sustainability and ecosystem service potential than the artificial green infrastructure. Currently, the ecological characteristics of urban wildness and its unique and irreplaceable values in ecology, culture economy and well-being have gained multi-disciplinary attention and been widely recognized. Some scholars have stated that urban wildness should be considered as an important opportunity to diversify the urban ecological networks, strengthen urban biodiversity conservation and deal with the intensification of the conflicts between human beings and nature. Although urban wildness has gradually become a hot topic and new frontier in ecology, the research on urban wildness within China and internationally is still in its infancy-there are a number of existing research gaps that could be addressed, including the identification of the spatial distribution, classification, ecological characteristics, ecosystem services and the mechanism for its protection and utilization, etc. These stated research gaps can directly lead to serious restrictions in the value judgment and protection decision-making of urban wilderness, resulting in the degradation or loss of the remnant urban wildness. This paper aims to systematically analyze the progress and trends of urban wildness ecology research, puts forward an in-depth analysis of the concept, classification and ecological characteristics of urban wildness, discusses the synergistic relationship between urban wildness and human beings, illustrates the opportunities and challenges of protecting wildness components, and then proposes the strategies for urban wilderness protection and restoration, as well as points out the key aspects for the future research and conservation/utilization. Due to the ecological civilization construction and the advance in adopting nature-based solutions in China, it is the best time to acknowledge urban wildness in depth and carry out practices of conservation and restoration. The contributions of this paper may provide a timely way to reconnect cities and nature, and provide scientific guidance for sustainable management of urban biodiversity, which is of great significance for the protection of urban natural capital and the enhancement of urban ecosystem resilience.