The left dorsomedial prefrontal cortex (dmPFC) is known to be associated with volition and motor function but is often overlooked in models of the neural bases of language. In this retrospective study, we reveal a robust statistical association between a rare language profile disproportionately affecting self-generated, but not externally cued, language production and damage to left dmPFC in a large (n = 307) neurosurgical database using both voxel-based and multivariate lesion-symptom mapping (VLSM, MLSM). This profile was not attributable to motivational or motor speech deficits. We further demonstrate that the probability of presenting with this profile is nearly 15 times higher following a resection in the dorsomedial prefrontal cortex than a resection elsewhere in the brain. Finally, we present a first person account of recovery from this language syndrome by a professionally trained linguist in the Supplementary Materials . These findings leverage a large dataset to add to the predominantly case-dominated literature demonstrating that damage specific to the dmPFC can cause a unique linguistic disturbance disproportionately affecting spontaneous speech, and provide a rare person-centered narrative of the experience of aphasia that is informative to scientists and clinicians alike. Overall, this work highlights the role of the left dmPFC, rarely included in dominant models of the neural bases of language, in the volitional control of fluent, self-generated speech.