Tsay Ting-kuei (Chinese: 蔡丁貴; Pe̍h-ōe-jī: Chhòa Teng-kùi; born 24 March 1949) is a Taiwanese civil engineering professor, political activist, and former government official. A professor at National Taiwan University in Taipei, he has conducted research in areas including coastal engineering and computational hydraulics. In politics, he served in various positions in the Chen Shui-bian administration in the mid-2000s, and rose to greater prominence for his protests in support of the Taiwan independence movement.