Zhang Guolao, also known as Zhang Guo, is a historical figure and one of the Eight Immortals. He is said to have been born during the middle or end of the 7th century CE, during the Tang Dynasty, and was a Taoist 'fangshi' (occultist-alchemist) who lived as a hermit on Zhongtiao Mountain. Zhang was portrayed with a strong love for wine and winemaking, and was a master of 'qigong' (life energy cultivation), able to survive for days without food and only a few sips of wine.

Zhang Guolao claimed to be several hundred years old by the time Empress Wu Zetian came to power. He traveled often on the back of a white donkey or mule, which he could fold away and place in his pocket after he was done traveling. He constantly declined invitations to the courts of the Tang Dynasty emperors, only agreeing to leave his hermitage when Wu Zetian asked. However, he died just as he reached the gates of the Temple of the Jealous Woman, his body swiftly decomposing. He was soon seen alive and well on Zhongtiao Mountain however.

Zhang Guolao was considered the most eccentric of the Eight Immortals, known as an entertainer and for his various whimsical acts.