Nguyễn Thị Hằng (Chinese: 阮氏晅, 1441 – 1505), also known as Grand Empress Dowager Trường Lạc, or courtesy name Ngọc Huyên (玉萱), is a famous queen consort of Lê dynasty. She was the wife of emperor Lê Thánh Tông and mother of emperor Lê Hiến Tông.. She was also grandmother of Emperor Lê Túc Tông and Emperor Lê Uy Mục.
Empress Trường Lạc was born in 1441 at Gia Miêu outer village, Tống Sơn district, Hà Trung local government, Thanh Hoa town. She was the daughter of the Duke Nguyễn Công Lộ and foster daughter of the officer Nguyễn Đức Trung. She has entered Lê dynasty's palace on July 1460 with rank Sung-nghi (充儀), lived at the palace of Vĩnh Ninh.
There are some unofficial reports stated that Empress Trường Lạc is actually a daughter of Nguyễn Trãi, a famous scholar under era of Emperor Lê Thái Tổ and Emperor Lê Thái Tông . All of her family members were exterminated in 1442 because of Mystery of Lệ Chi Viên, one of the biggest mysteries in Vietnamese history. She and her brother Nguyễn Anh Vũ luckily survived and then was adopted by officer Nguyễn Đức Trung of Gia Miêu Nguyễn clan. And later, in 1470, she became a Imperial consort Quy of Emperor Lê Thánh Tông.