The insular cortex has emerged as a key region implicated in a wide array of cognitive, emotional, and sensory processes. The anterior part of the insula (AIC) is central to emotional awareness, decision-making, and interoception, while the posterior insula (PIC) is more associated with somatosensory processing. The insula acts as a functional hub within the salience network and integrates homeostatic, affective, and cognitive information; thus, its role in different mental disorders seems to be prominent. Altered structure and connectivity of the insular cortex are evident in several psychiatric conditions. In schizophrenia, reductions in insular volume—especially on the left—correlate with hallucinations, emotional dysregulation, and cognitive deficits. Bipolar and major depressive disorders exhibit AIC volume loss and aberrant connectivity patterns linked to impaired affect regulation and interoceptive awareness. Anxiety disorders show functional hyperactivity of the insula, especially in response to fear-inducing stimuli, though findings on structural changes are mixed. Overall, growing evidence underscores the insular cortex’s central role in psychiatric pathophysiology and highlights its potential as a target for future diagnostic and therapeutic strategies.