Seodaemun District is one of the 25 districts of Seoul, South Korea.
Seodaemun has a population of 313,814 and has a geographic area of 17.61 km², and is divided into 14 dong. Seodaemun is located in northwestern Seoul, bordering the city districts of Eunpyeong to the northwest, Mapo to the southwest, Jung to the southeast, and Jongno to the east.
Seodaemun is part of the Seongjeosimni area and is named after Donuimun, one of the Eight Gates of Seoul which was formerly located within the district. Seodaemun is home to Seodaemun Independence Park, which contains several historic monuments and buildings such as the Seodaemun Prison museum and the Independence Gate.
Moon Seok-Jin of the Democratic Party has been the mayor of Seodaemun since July 2010.