The issue of loneliness among single city youths who are beyond the conventional age for marriage has emerged, but has not received sufficient attention. Using the consensual qualitative research method, this study analyzed the phenomenon. Interview data revealed three domains: loneliness experience, loneliness causes, and loneliness coping. Within the loneliness experience domain, there were three subdomains: loneliness mentality, stage change, and impact of loneliness. Overall, loneliness was regarded as a negative psychological experience; loneliness levels tended to change during different life stages; loneliness had much more negative impacts than positive impacts. Within the loneliness causes domain, there were five subdomains: state of social interaction, surrounding environment, personality, life situation, and growth experience. Lack of a romantic partner and low-quality social interactions were two most common causes of loneliness. Within the loneliness coping domain, there were two subdomains: active adjustment as well as acceptance and endurance. Self-adjustment and seeking support were two most common categories of coping strategies. These results have important implications for understanding and reducing loneliness among single city youths who are beyond the conventional age for marriage.