• meets Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) criteria for OCD with a moderate level of severity as defined by a Yale-Brown Obsessive Compulsive Scale (YBOCS) score of at least 18.

• stable on Serotonin Re-uptake Inhibitor (SRI) medication for at least 8 weeks prior to (with plans to continue throughout) the study Note: Medications that are known to increase cortical excitability (e.g., buprorion, maprotiline, tricyclic antidepressants, classical antipsychotics) or to have an inhibitory effect on brain excitability (e.g., anti-convulsants, benzodiazepines, and atypical antipsychotics), or any other medications with relative hazard for use in TMS will be allowed upon review of medications and/or motor threshold determination by TMS specialist.

• failed at least 1 prior trial of standard first-line OCD treatment per American Psychological Association (APA) Practice Guidelines (serotonin reuptake inhibitor \[SRI\] or cognitive behavioral therapy with exposure and response prevention)OR had refused these treatments for individual reasons.

• capacity to provide informed consent.

• ability to tolerate clinical study procedures.

• successfully complete the screening forms at the Stanford Center for Cognitive and Neurobiological Imaging (CNI) without any contraindications.