<p>This essay examines Kazuo Ishiguro’s <i>Klara and the Sun</i> (2021) as a case study in loneliness and posthuman sociality. Through interpreting this novel, I pose two key research questions: First, what does posthuman sociality mean, and how does Ishiguro’s novel present it? Second, what is the relationship between posthuman sociality and loneliness as reflected in <i>Klara and the Sun</i>? In other words, can posthuman sociality stave off loneliness in a technologized world where people feel disconnected, or does loneliness unmask the illusion of posthuman sociality? In response to these questions, my essay first reviews previous scholarship on an inclusive version of sociality and situates my research within these debates to further clarify this notion. Specifically, I draw on Rosi Braidotti’s posthuman theory of relationality to elucidate the idea of “posthuman sociality.” Next, my essay employs <i>Klara and the Sun</i> as a case study. I argue that posthuman sociality in Ishiguro’s novel disrupts hierarchical divides between AI and humans. It nurtures affective attachments with AIs, allowing us to acquire a sense of belonging and emotional support within an expanded community, serving as an antidote to loneliness. However, the novel also reveals the limitations of this conception of sociality, suggesting that human–machine interactions can never supplant interpersonal relationships in meeting our social needs. Here, loneliness may act as a lens that magnifies the problems of posthuman sociality. By combining insights from posthumanism, affect studies, and critical AI studies, my research on Ishiguro’s novel explores the extent to which AI can extend and transform our perspectives on social interactions, as well as how loneliness plays a role in deterring this extension.</p>