Creator's Description: This paper focuses on fertility transitions that have recently occurred in the Tibet Autonomous Region (TAR) and among Tibetan exiles living in South Asia. The Tibetan cases are compared with fertility transitions in China, India, and historical Europe with respect to (1) the social and demographic forces that shaped pre-transitional levels of fertility, (2) frequencies of marriage and non-marital fertility, (3) the timing, duration, and magnitude of the fertility transitions, and (4) the impact that fertility transitions have had on sex ratios. The analysis shows that fertility in pre-transitional Tibetan societies was more similar to Europe than China or India, due to factors related to the family system and the limitations it imposed on marriage; that although Tibetan fertility transitions started comparatively late in time, they proceeded at an extraordinarily rapid pace; and that unlike in China and India, fertility transitions among Tibetans have not been accompanied by increasingly skewed sex ratios that favor males.