Functional Neurological Disorders (FNDs) are characterized by symptoms of altered voluntary motor or sensory function with clinical findings providing evidence of incompatibility between the symptoms and recognized neurological or medical conditions. FNDs are highly prevalent and associated with significant morbidity, health care costs, and even mortality. In some respects, this group of conditions sits at the intersection of neurology and psychiatry, but the majority of cases first come to the attention of neurologists. Management is complex and requires interdisciplinary approaches. Given the disability caused by the symptoms, and the high cost in healthcare utilization and loss of productivity, FNDs amount to a significant missed opportunity for therapeutic intervention and therefore, a healthcare crisis. Diagnosis and management of FNDs remain very challenging. Diagnostic criteria have been proposed but they are not universally agreed upon. Diagnosis is based on positive clinical findings, and can be supported by laboratory or ancillary investigation findings. Certain FND subtypes are more difficult to correctly diagnose than others. More importantly, laboratory-supported diagnosis is possible, and biomarkers can be developed, but significantly more research is needed in these areas to advance clinical management of FNDs. Therapies exist and have been studied in select populations but gathering high-level evidence through clinical trials is hampered by limitations in available outcome measures. Differential responses to treatments have been recorded, and thus, prediction of aggregate treatment response has been difficult. This FOA invites researchers to submit prospective clinical projects that address critical needs for clinical trial readiness in FNDs. Projects appropriate for this FOA include the validation of biomarkers, endpoints and clinical outcome assessments (COA) that are fit-for-purpose and have a defined context of use for clinical trials.