query: Who is the longest ruling emperor of China?
passage: Kangxi Emperor
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.
passage: Emperor Xian of Han
Emperor Xian of Han (2 April 181 – 21 April 234), personal name Liu Xie, courtesy name Bohe, was the 14th and last emperor of the Eastern Han dynasty in China. He reigned from 28 September 189 until 11 December 220.[4][5]