Background <p>Rumination—a passive, repetitive focus on negative thoughts and emotions—is a key risk factor for the onset and recurrence of depression. While prior studies have linked rumination to altered functional connectivity (FC) in brain networks, most relied on self-reported measures and resting-state fMRI, potentially missing key neural dynamics during active ruminative states.</p> Methods <p>We recruited 43 patients with major depressive disorder (MDD) and 42 matched healthy controls (HCs). Using a validated rumination state task (RST), we induced active rumination and distraction states during fMRI scanning. We constructed whole-brain functional connectomes and examined both FC patterns and a graph-theoretical feature (eigenvector centrality) across conditions. We also examined associations between the graph-theoretical feature and depressive symptom severity.</p> Results <p>Both MDD patients and HCs exhibited enhanced FC between the core and medial temporal lobe (MTL) subsystems of the default mode network (DMN) during rumination compared to distraction. However, edge-level analyses revealed group differences: HCs showed greater FC increases between the ventral attention network (VAN) and the DMN-MTL subsystem. We found a significant interaction effect regarding eigenvector centrality in a VAN node (Par_Med_4_R). During rumination, patients with MDD exhibited elevated eigenvector centrality compared to distraction, whereas HCs did not. This elevation correlated positively with depression severity.</p> Conclusions <p>This study provides the first comprehensive characterization of the active rumination connectome in MDD. Results highlight a shared DMN mechanism and a VAN-specific topological alteration in MDD, supporting the theory that excessive automatic constraints from attentional systems may drive maladaptive rumination.</p> Clinical trial number <p>Not applicable</p>