Background: Men with advanced prostate cancer (APC) experience high mortality and severely impacted quality of life due to the disease itself as well as its therapies, with Black men facing the highest disease burden. The treatment landscape for APC is rapidly changing; however, little is known about the real-life experience of men receiving new therapies. There is an urgent need to identify disparities in treatment patterns and outcomes in advanced disease, based on patient and country demographics. The International Registry for Men with Advanced Prostate Cancer (IRONMAN) is uniquely equipped to meet these needs. Methods: IRONMAN is a population-based prospective cohort of men with newly diagnosed metastatic hormone-sensitive (mHSPC) and castration-resistant (CRPC) prostate cancer aiming to enroll 5,000 men across 16 countries (Australia, the Bahamas, Barbados, Brazil, Canada, Ireland, Jamaica, Kenya, Nigeria, Norway, South Africa, Spain, Sweden, Switzerland, United Kingdom, Untied States). Patients are followed prospectively for overall survival, clinically significant adverse events, changes in cancer treatments, biomarkers, and Patient-Reported Outcome Measures (PROMs). Data is collected via longitudinal electronic questionnaires from patients and providers as well as blood samples and medical records. IRONMAN is currently enrolling in 10 countries at 103 sites. Sites were selected to create a diverse cohort across race/ethnicity, rural/urban populations, socioeconomic factors, and geographic regions. Of the first 1,865 men enrolled to date, 60% have mHSPC and 40% have CRPC; overall, 9% of men (18% in the US) self-identify as Black and 82% identify as white (78% in the US). 60% (N = 1,111) of this cohort has been enrolled outside of the US, and the median age at study entry is 70 years. The distribution and demographics of patients are continuously monitored to inform ongoing enrollment efforts. The IRONMAN Diversity Working Group meets monthly to discuss barriers and strategies to enhance enrollment of a racially and ethnically diverse population. The Low- and Middle-Income Country Working Group addresses the unique needs of men being recruited from the Caribbean and African sites in addition to supporting broad oncology efforts in these regions. These efforts support IRONMAN’s larger goal to investigate disparities in the care of patients with APC, having potential implications for decreasing racial disparities in survival outcomes. Clinical trial information: NCT03151629.