Parkinson's disease (PD) is a neurological condition, which affects the brain. Some symptoms of PD are tremors, stiffness, and slowness of movement. The purpose of this study is to assess how safe and effective ABBV-951 is in treating participants with Parkinson's disease in real world setting. ABBV-951 is an approved drug being developed for the treatment of PD in Japan. Approximately 250 adult participants over 15 years with a diagnosis of PD who are prescribed ABBV-951 by their physicians will be enrolled in this study across Japan. Participants will receive ABBV-951 as prescribed their physician and followed for 52 weeks. There is expected to be no additional burden for participants in this trial. Study visits may be conducted on-site or virtually as per standard of care.