Dongdaemun District is one of the 25 districts of Seoul, South Korea.
Dongdaemun has a population of 346,770 and has a geographic area of 14.22 km², and is divided into 14 dong. Dongdaemun is located in northeastern Seoul, bordering the city districts of Seongbuk to the northwest, Jongno to the west, Seongdong to the south, Gwangjin to the southeast, and Jungnang to the east.
Dongdaemun is part of the Seongjeosimni area and is named after Heunginjimun, one of the Eight Gates of Seoul which is not located within the district. Dongdaemun is home to the University of Seoul, Cheongnyangni station, and to Gyeongdong Market, one of the largest herbal medicine and agricultural markets in South Korea.
Yoo Deok-yeol of the Democratic Party has been the mayor of Dongdaemun since July 2010.