title: Kangxi Emperor
context: The Kangxi Emperor's reign of 61 years makes him the longest-reigning emperor in Chinese history (although his grandson, the Qianlong Emperor, had the longest period of de facto power) and one of the longest-reigning rulers in the world.[1] However, since he ascended the throne at the age of seven, actual power was held for six years by four regents and his grandmother, the Grand Empress Dowager Xiaozhuang.
question: Who is the longest ruling emperor of China?
answers: Kangxi