Emperor Xuanzong of Tang ( 8 September 685 – 3 May 762), also commonly known as Emperor Ming of Tang, personal name Li Longji, known as Wu Longji from 690 to 705, is the seventh emperor of the Tang dynasty in China, reigning from 712 to 756.

His reign of 43 years is the longest during the Tang Dynasty.

In the early half of his reign he is a diligent and astute ruler, ably assisted by capable chancellors like Yao Chong and Song Jing, and is credited with bringing Tang China to a pinnacle of culture and power.

Emperor Xuanzong, however, is blamed for over-trusting Li Linfu, Yang Guozhong and An Lushan during his late reign, with Tang's golden age ending in the Anshi Rebellion.

This is the decline of the Tang Dynasty.