Abstract Introduction Sleep duration is a reliable predictor of health outcomes. However, average sleep duration varies significantly across countries, with Japan and other East Asian countries reporting the shortest average sleep durations, and some Western European countries the longest. These disparities exceed 90 minutes, raising the question of whether countries with shorter sleep durations may be suffering from worse health. These striking differences highlight the need for cross-cultural research to better understand the relationships between culture, sleep duration, and health. Methods We conducted a pre-registered cross-national survey of approximately 5000 participants across 20 countries regarding sleep duration and current health using Qualtrics sampling panels. We used multilevel modeling to explore the relationships between self-reported sleep duration and health both within and between countries. Results France had the longest average sleep duration at 7 hours 52 minutes, whereas Japan had the shortest average sleep duration at 6 hours and 18 minutes for a range of 94 minutes. Within countries, participants with longer sleep duration had better health on a health composite variable that included mental health, subjective health, and chronic conditions (b = 0.09, 95%CI = [0.07-0.10], p = < 0.001). In contrast, national sleep duration did not predict health (b = 0.09, 95%CI = [-0.10, 0.27], p = 0.349). ANOVA revealed a significant difference between sleep dura