Zaiyuan (1816 1861) was a Manchu prince of the Qing Dynasty. He was one of the eight regents appointed by the Xianfeng Emperor to assist his successor, the Tongzhi Emperor. His title was Prince Yi of the First Rank ( ).
Zaiyuan was born of the Manchu Aisin Gioro clan as a fifth generation descendant of Yunxiang, the 13th son of the Kangxi Emperor. He inherited his ancestors' title of "Prince Yi of the First Rank" in 1852.
Zaiyuan took up important positions during the reign of the Xianfeng Emperor, including being a minister in the Imperial Clan Court and imperial guard commander. In 1860 during the Second Opium War, as the British and French armies closed in on Beijing, Zaiyuan fled together with the Xianfeng Emperor to Rehe Province.
Before the Xianfeng Emperor died in 1861, he appointed Zaiyuan, Sushun, Duanhua and five others as regents to assist his son and successor, the Tongzhi Emperor. Later that year, Empress Dowager Cixi and Prince Gong initiated the Xinyou Coup and seized power from the eight regents. Zaiyuan was arrested in Beijing and imprisoned. He was given a piece of white silk cloth to commit suicide by hanging himself with the cloth. After Zaiyuan's death, his princely title was inherited by Zaidun ( ), a distant cousin.