This chapter focuses on climate change–induced societal collapse that occurred in the common era. It discusses the emergence and collapse of the Roman Empire. This starts with the story of the Western Roman Empire, its great achievements, its rise to the pinnacle of world dominance, and the challenges it faced. This is followed by the decline and fall of the empire, and the supporting evidence that show the contribution of climate change to closing this remarkable era in human history. The discussion also highlights the debilitating effect of climate change on the Eastern Roman Empire. The chapter, then, moves to the story of the Khmer Empire centered around the city of Angkor and beyond. A discussion of the hydraulic achievements of such a civilization, and how climate deterioration affected that elaborate system leading to its collapse, is included. The chapter concludes with the stories of several Chinese dynasties such as the Han, the Tang, the Song, the Yuan, and the Ming dynasties. Then, the chapter closes with a discussion of studies on the statistical association between climate disturbance and dynastic collapse in China.