We investigated the prevalence of persecutory, grandiose, reference, control, and religious delusions in adult clinical populations worldwide and whether they differed according to country characteristics or age, gender, or year of publication. 123 studies met inclusion criteria, across 30 countries; 102 (115 samples, n = 20,979) were included in the main random-effects meta-analysis of studies measuring multiple delusional themes (21 in a separate analysis of studies in recording a single theme). Persecutory delusions were most common (pooled point estimate: 64.5%, CI = 60.6–68.3, k = 106, followed by reference (39.7%, CI 34.5–45.3, k = 65), grandiose (28.2, CI 24.8–31.9, k = 100), control 21.6%, CI 17.8–26.0, k = 53), and religious delusions 18.3%, CI 15.4–21.6, k = 50). Data from studies recording one theme were broadly consistent with these findings. There were no effects for study quality or publication date. Prevalences were higher in samples exclusively with psychotic patients but did not differ between developed and developing countries, or by country individualism, power distance, or prevalence of atheism. Religious and control delusions were more prevalent in countries with higher income inequality. We hypothesize that these delusional themes reflect universal human dilemmas and existential challenges.