Systematic changes have been observed in the functional architecture of the human brain with advancing age. However, functional connectivity (FC) is also a powerful feature to detect unique “connectome fingerprints,” allowing identification of individuals among their peers. Although fingerprinting has been robustly observed in samples of young adults, the reliability of this approach has not been demonstrated across the lifespan. We applied the fingerprinting framework to the Cambridge Centre for Ageing and Neuroscience cohort ( n = 483 aged 18 to 89 years). We found that individuals are “fingerprintable” (i.e., identifiable) across independent functional MRI scans throughout the lifespan. We observed a U-shape distribution in the strength of “self-identifiability” (within-individual correlation across modalities), and “others-identifiability” (between-individual correlation across modalities), with a decrease from early adulthood into middle age, before improving in older age. FC edges contributing to self-identifiability were not restricted to specific brain networks and were different between individuals across the lifespan sample. Self-identifiability was additionally associated with regional brain volume. These findings indicate that individual participant-level identification is preserved across the lifespan despite the fact that its components are changing nonlinearly. Author Summary Important interindividual differences are increasingly identified in functional connectivity studies. However, most of the work to date has focused on samples of younger adults, ignoring older individuals in which brains undergo significant transformation. Here, we examine individual-level patterns of functional connectivity—that is, connectome fingerprints—across the adult lifespan. Our results suggest that connectome fingerprints can reliably predict individuals from independent brain scans across the lifespan. Additionally, regions contributing to fingerprints differed from person to person, emphasizing the extent of interindividual differences in the brain. Specific patterns of brain volume, associated with normative age-related atrophy, may impact the identification of individual-specific functional connectivity patterns. Our findings highlight the importance of interindividual variability in functional connectivity, regardless of participant age, when assessing individual differences in brain function.