| Emperor Đồng Khánh 同慶帝 | |
| Father: | Nguyễn Phúc Hồng Cai (son of Thiệu Trị) |
| Mother: | Concubine Bùi Thị Thanh |
| Spouse: | 11 concubines |
| Issue: | 9 including 6 sons and 3 daughter prince Nguyễn Phúc Bửu Đảo |
| Birth Date: | 19 February 1864 |
| Birth Place: | Imperial City of Huế, Đại Nam |
| Death Place: | Imperial City of Huế, Annam, French Indochina |
| Place Of Burial: | Tư Lăng |
| Full Name: | Nguyễn Phúc Ưng Thị Nguyễn Phúc Ưng Kỷ Nguyễn Phúc Ưng Đường Nguyễn Phúc Biện |
| Succession: | Emperor of Đại Nam under French protectorate of Annam and Tonkin |
| Reign: | 19 September 1885 – 28 January 1889 |
| Predecessor: | Hàm Nghi |
| Successor: | Thành Thái |
| Succession1: | Emperor of the Nguyễn dynasty |
| Reign1: | 19 September 1885 – 28 January 1889 |
| Predecessor1: | Hàm Nghi |
| Successor1: | Thành Thái |
| House: | Nguyễn Phúc |
| Era Name: | Đồng Khánh |
| Era Dates: | 1885–1889 |
| Temple Name: | Cảnh Tông |
| Posthumous Name: | Hoằng Liệt Thông Thiết Mẫn Huệ Thuần Hoàng Đế (弘烈聰哲敏惠純皇帝) Phối Thiên Minh Vận Hiếu Đức Nhân Vũ Vĩ Công Hoằng Liệt Thông Thiết Mẫn Huệ Thuần Hoàng Đế (配天明運孝德仁武偉功弘烈聰哲敏惠純皇帝) (1916) |
Đồng Khánh (pronounced as /vi/, Vietnamese: [[:wikt:同|同]][[:wikt:慶|慶]], lit. "collective celebration"; 19 February 1864 – 28 January 1889), born Nguyễn Phúc Ưng Kỷ (阮福膺祺) or Nguyễn Phúc Ưng Đường (阮福膺禟), also known as Chánh Mông (正蒙), was the ninth emperor of the Nguyễn dynasty of Vietnam. He reigned four years between 1885 and 1889. His royal temple name was Cảnh Tông (景宗).
Đồng Khánh was born on 19 February 1864 in the Imperial City of Huế. His childhood name was Chánh Mông because he was brought up in Chánh Mông palace. Đồng Khánh was the eldest son of Prince Nguyễn Phúc Hồng Cai, a son of emperor Thiệu Trị, and his concubine Bùi Thị Thanh.
As his uncle, Emperor Tự Đức, had no children, Đồng Khánh was adopted and given the title Kiên Giang quận công (Duke of Kiên Giang).
After the French armies captured the city of Huế and the Imperial city fell to the French, the court regents Nguyễn Văn Tường and Tôn Thất Thuyết took the young Emperor Hàm Nghi and escaped from the Purple Forbidden City of Huế, and took him to Tân Sở in the mountains as the figurehead of a revolutionary movement against the French. To take away the legitimacy of Hàm Nghi, general de Courcy and résident de Champeaux of France asked the empress dowager Nghi Thiên to enthrone Hàm Nghi's elder half brother prince Nguyễn Phúc Ưng Kỷ. On 19 September 1885 with the backing of the governor of Annam, Prince Nguyễn Phúc Ưng Kỷ was crowned as the ninth emperor of Đại Nam with the era name of Đồng Khánh.Đồng Khánh was pro-French, which was noted in the diary of Trần Trọng Kim:
On 28 January 1889, Đồng Khánh died aged 24 after reigning for three years. He was granted the posthumous name Hoằng Liệt Thông Thiết Mẫn Huệ Thuần Hoàng Đế (弘烈聰哲敏惠純皇帝), with the temple name Cảnh Tông (景宗).In 1916, his son the Emperor Khải Định granted him the name Phối Thiên Minh Vận Hiếu Đức Nhân Vũ Vĩ Công Hoằng Liệt Thông Thiết Mẫn Huệ Thuần Hoàng Đế (配天明運孝德仁武偉功弘烈聰哲敏惠純皇帝). He was buried in Tư Lăng mausoleum (思陵), which is located at Dương Xuân Thượng village, Hương Thuỷ commune, Thừa Thiên Province.