Inclusion Criteria:  DSM-5 diagnosis of major depressive disorder confirmed using the Mini International Neuropsychiatric Interview (MINI30) Axis 1 and mood modules Met criteria for treatment-resistant MDD during the current major depressive episode documented in the MGH Antidepressant Treatment History Questionnaire (ATRQ31), which will be defined as being non-responders (less than 50% of symptom improvement) to two or more depression treatment trials of adequate dose and duration as defined by the MGH ATRQ,as well as an adequate course of TMS treatment using standard targeting approaches (e.g. 5-cm, 5.5-cm, F3) at least moderate depression severity, operationalized as Montgomery-Asberg Depression Rating Scale (MADRS) score ≥ 20  Exclusion Criteria:  Ever met criteria for a psychotic disorder (Sz, SzAff, Bipolar disorder); anorexia nervosa or bulimia nervosa within the last year Unstable medical condition by history, physical exam or laboratory results Currently pregnant or breastfeeding women; fecund women not using adequate contraceptive methods or with plan to become pregnant Contraindications to MRI (based on metal screening form) Meets criteria for claustrophobia Recent drug or alcohol use disorder with DSM-5 specifier of moderate or severe within 6 months, or mild within 2 months; lifetime history of IV drug use Actively suicidal, as defined by expressive ideation with a plan or with suicidal ideation that requires immediate medical or treatment intervention; A neurological or neuromuscular disorder; 9) Require medications for a general medical condition that contraindicate the TMS treatment Prior non-response to ECT, vagal nerve stimulation (VNS) or deep brain stimulation (DBS) History of ketamine treatment within 6 mo History of monoamine oxidase inhibitor (MAOI) within the past month Lacks capacity to consent Taking medications that increase the risk of seizures. For TMS-naïve subjects, prior history of TMS treatment. For patients on permitted concomitant psychotropic agents (antidepressants, anticonvulsants, benzodiazepines, hypnotics, opiates, triiodothyronine (T3), modafinil, psychostimulants, buspirone, melatonin, omega-3 fatty acids, folate, l-methylfolate, s-adenosyl methionine, lithium) dosing must be stable for at least four weeks prior to study entry and patients must agree to continue at the same dose during the study