Inclusion Criteria:  Participant has sufficient visual acuity without the use of eyeglasses (contact lens use is acceptable) to accurately assess their facial lines. Participant has severe GL at maximum frown as assessed by both the investigator and participant using the Facial Wrinkle Scale - Glabellar Lines (FWS-GL) at Baseline.  Exclusion Criteria:  History of known immunization to any botulinum toxin serotype. History of known hypersensitivity to any botulinum toxin serotype, or any other constituents of the study drug or its excipients, and/or other products in the same class.  Presence or history of any medical condition that may place the participant at increased risk following exposure to OnabotA X or interfere with the study evaluation, including:  Diagnosed myasthenia gravis, Lambert-Eaton syndrome, amyotrophic lateral sclerosis, or any other significant disease that might interfere with neuromuscular function History of facial nerve palsy Infection or dermatological condition at the site of study drug injection Marked facial asymmetry, dermatochalasis, deep dermal scarring, excessively thick sebaceous skin, excessively photodamaged skin, or the inability to substantially lessen facial lines even by physically spreading them apart Any eyebrow or eyelid ptosis at baseline or Day 1 as determined by the investigator