Rapid urbanisation has marked recent human history with more than 50% of the world's population now living in urban areas while the percentage and the overall population are still growing. Resource consumption is conglomerated in urban settlements which depend primarily on externally supplied and often fossil-based products. With the aim to transform cities sustainably from resource sinks to regenerative hubs, the concept of the Urban Bioeconomy poses a potential alternative to the current economic system. While the concept has been in discussion among practitioners and a few researchers, its meaning is not well established. Therefore, this study proposes a definition of the Urban Bioeconomy based on a systematic literature review, which focused on identifying its components, impacts and potential synergies within bioeconomic sectors, namely the ‘Urban Bio-Symbiosis’. This work highlights existing and emerging bioeconomic components within cities such as urban farming, biowaste valorisation methods and green infrastructure techniques. It outlines opportunities and challenges of the Urban Bioeconomy by presenting potential positive and negative environmental, economic, social and health impacts. Based on these results, it identifies the potential of the Urban Bio-Symbiosis and Resource Circularity as promising solutions to bring about synergistic effects between different urban bioeconomic components themselves and with the other parts of the economy. By proposing a definition of the Urban Bioeconomy, this work sets the ground for further research in this field.