Yin (Chinese: 尹; pinyin: Yǐn) is a Chinese surname. In 800 BCE, Bo Jifu, a renowned judge during the reign of Zhou Xuan Wang, held the position of Yin (equivalent to First Minister, most favored Minister, or Lord Protector), and changed his name to Yin Jifu. During the era of the Imperial Examination System, three other magistrates took on the surname Yǐn (尹) to denote their Imperial rank and favoured status. The Korean surname Yoon and the Vietnamese surname Doãn are derived from Yin and traditionally written in the same Chinese character.