Background: Adolescents are often noted to have an increased risk of death during pregnancy or childbirth compared with older women, but the existing evidence is inconsistent and in many cases contradictory. We aimed to quantify the risk of maternal death in adolescents by estimating maternal mortality ratios for women aged 15–19 years by country, region, and worldwide, and to compare these ratios with those for women in other 5-year age groups. Methods: We used data from 144 countries and territories (65 with vital registration data and 79 with nationally representative survey data) to calculate the proportion of maternal deaths among deaths of females of reproductive age (PMDF) for each 5-year age group from 15–19 to 45–49 years. We adjusted these estimates to take into account under-reporting of maternal deaths, and deaths during pregnancy from non-maternal causes. We then applied the adjusted PMDFs to the most reliable age-specific estimates of deaths and livebirths to derive age-specific maternal mortality ratios. Findings: The aggregated data show a J-shaped curve for the age distribution of maternal mortality, with a slightly increased risk of mortality in adolescents compared with women aged 20–24 years (maternal mortality ratio 260 [uncertainty 100–410] vs 190 [120–260] maternal deaths per 100 000 livebirths for all 144 countries combined), and the highest risk in women older than 30 years. Analysis for individual countries showed substantial heterogeneity; some showed a clear J-shaped curve, whereas in others adolescents had a slightly lower maternal mortality ratio than women in their early 20s. No obvious groupings were apparent in terms of economic development, demographic characteristics, or geographical region for countries with these different age patterns. Interpretation: Our findings suggest that the excess mortality risk to adolescent mothers might be less than previously believed, and in most countries the adolescent maternal mortality ratio is low compared with women older than 30 years. However, these findings should not divert focus away from efforts to reduce adolescent pregnancy, which are central to the promotion of women's educational, social, and economic development. Funding: WHO, UN Population Fund.