Nguy?n Phúc H?ng Cai (????, 13 December 1845 – 15 May 1876) was a prince of Nguy?n dynasty, Vietnam.
He was the father of three emperors: Ki?n Phúc, Ð?ng Khánh and Hàm Nghi.
H?ng Cai was the twenty-sixth son of Thi?u Tr?, and his mother was Truong Th? Vinh.
He was a filial son and liked studying.
He was granted the title Kiên Qu?c Công (???, "Duke of Kiên") in 1865.
T? Ð?c had no child, and adopted his two sons, Ung Ðang and Ung Th?, whom later became Emperor Ki?n Phúc and Emperor Ð?ng Khánh respectively.
H?ng Cai died in 1876 and received the posthumous name Thu?n Ngh? (??).
He was buried in Huong Th?y.
In 1885, Ð?ng Khánh ascended the throne, and granted him the title Kiên Vuong (??, "Prince of Kiên") posthumously.
Later, his title was elevated to Kiên Thái Vuong (???, "King Father Kiên") in 1888.