당현종, or Emperor Xuan Zong of Tang, was the seventh emperor of the Tang Dynasty in China, ruling from 712 to 756 AD. He is known for his long and prosperous reign, which is often considered a high point in Chinese history. His rule was marked by cultural flourishing, economic stability, and the expansion of the empire. During his reign, Xuanzang promoted the arts, literature, and trade, leading to a vibrant cultural exchange. However, his later years were marred by the An Lushan Rebellion, which significantly weakened the Tang Dynasty and led to its eventual decline.