Seoul Subway Line 5 of the Seoul Metropolitan Subway, dubbed the purple line, is a long line crossing from west to the east across the Seoul National Capital Area, South Korea. It is one of two subway lines in Seoul to cross under the Han River, which is done at two points. The main line runs through to Hanam Geomdansan Station while the branch line from Gangdong Station terminates at Macheon Station. In 2019, Line 5 carried an annual ridership of 334 million or about 915,000 passengers per day.

The Seoul Metropolitan Subway is a metropolitan railway system consisting of 23 rapid transit, light metro, commuter rail and people mover lines located in northwest South Korea. The system serves most of the Seoul Metropolitan Area including the Incheon metropolis and satellite cities in Gyeonggi province. Some regional lines in the network stretch out beyond the Seoul Metropolitan Area to rural areas in northern Chungnam province and western Gangwon Province, that lie over 100 km (62 mi) away from the capital.