Nam Định ( listen) is a large city in the Red River Delta of northern Vietnam. It is the capital of Nam Định Province. The city of Nam Định is 90 km southeast of Vietnam's capital, Hanoi. From August 18–20 of each year, there is a festival held in Nam Định called the Co Trach. This celebration honors General Trần Hưng Đạo, a 13th-century national hero who led Vietnamese forces to victory over the invading Mongols.