OBJECTIVE To investigate associations between age at natural menopause, particularly premature ovarian insufficiency (POI) (natural menopause before age 40 years), and incident type 2 diabetes (T2D) and identify any variations by ethnicity. RESEARCH DESIGN AND METHODS We pooled individual-level data of 338,059 women from 13 cohort studies without T2D before menopause from six ethnic groups: White (n = 177,674), Chinese (n = 146,008), Japanese (n = 9,061), South/Southeast Asian (n = 2,228), Black (n = 1,838), and mixed/other (n = 1,250). Hazard ratios (HRs) of T2D associated with age at menopause were estimated in the overall sample and by ethnicity, with study as a random effect. For each ethnic group, we further stratified the association by birth year, education level, and BMI. RESULTS Over 9 years of follow-up, 20,064 (5.9%) women developed T2D. Overall, POI (vs. menopause at age 50–51 years) was associated with an increased risk of T2D (HR 1.31; 95% CI 1.20–1.44), and there was an interaction between age at menopause and ethnicity (P < 0.0001). T2D risk associated with POI was higher in White (1.53; 1.36–1.73), Japanese (4.04; 1.97–8.27), and Chinese women born in 1950 or later (2.79; 2.11–3.70); although less precise, the risk estimates were consistent in women of South/Southeast Asian (1.46; 0.89–2.40), Black (1.72; 0.95–3.12), and mixed/other (2.16; 0.83–5.57) ethnic groups. A similar pattern, but with a smaller increased risk of T2D, was observed with early menopause overall (1.16; 1.10–1.23) and for White, Japanese, and Chinese women born in 1950 or later. CONCLUSIONS POI and early menopause are risk factors for T2D in postmenopausal women, with considerable variation across ethnic groups, and may need to be considered in risk assessments of T2D among women.