Loneliness is a multifaceted construct that engages a range of neural systems implicated in processing social cues, navigating interpersonal relationships, and engaging with the external world. In this chapter, we synthesize findings from neuroimaging studies that investigate the neural correlates of loneliness, organizing the discussion into two main sections. The first section provides an overview of studies using task-based paradigms to examine brain activity in response to external stimuli. This top-down approach has revealed that loneliness is associated with heightened sensitivity to social threats, dysregulated responses to social rewards, and altered representations of the self and others. The second section discusses studies employing naturalistic and resting-state paradigms to uncover neural signatures of loneliness that extend beyond specific task demands. These studies underscore the complex and distributed nature of loneliness-related brain activity, revealing distinct large-scale connectivity patterns associated with the experience of loneliness. Together, these findings illustrate the contributions of neuroimaging to our understanding of the psychological mechanisms underlying loneliness. We conclude by outlining future research directions, emphasizing the importance of integrative, multi-method approaches to further unravel the complexities of how loneliness is represented and processed in the human brain.