BACKGROUND: Oncology randomized controlled trials (RCTs) are increasingly global in scope. Whether authorship is equitably shared between investigators from high-income countries (HIC) and low-middle/upper-middle incomes countries (LMIC/UMIC) is not well described. The authors conducted this study to understand the allocation of authorship and patient enrollment across all oncology RCTs conducted globally. METHODS: A cross-sectional retrospective cohort study of phase 3 RCTs (published 2014-2017) that were led by investigators in HIC and recruited patients in LMIC/UMIC. FINDINGS: During 2014-2017, 694 oncology RCTs were published; 636 (92%) were led by investigators from HIC. Among these HIC-led trials, 186 (29%) enrolled patients in LMIC/UMIC. One-third (33%, 62 of 186) of RCTs had no authors from LMIC/UMIC. Forty percent (74 of 186) of RCTs reported patient enrollment by country; in 50% (37 of 74) of these trials, LMIC/UMIC contributed <15% of patients. The relationship between enrollment and authorship proportion is very strong and is comparable between LMIC/UMIC and HIC (Spearman's ρ LMIC/UMIC 0.824, p < .001; HIC 0.823, p < .001). Among the 74 trials that report country enrollment, 34% (25 of 74) have no authors from LMIC/UMIC. CONCLUSIONS: Among trials that enroll patients in HIC and LMIC/UMIC, authorship appears to be proportional to patient enrollment. This finding is limited by the fact that more than half of RCTs do not report enrollment by country. Moreover, there are important outliers as a significant proportion of RCTs had no authors from LMIC/UMIC despite enrolling patients in these countries. The findings in this study reflect a complex global RCT ecosystem that still underserves cancer control outside high-income settings.