Seohae Bridge, Cable-stayed road bridge over the Yellow Sea between Dangjin and Pyeongtaek, South Korea

Seohae Bridge is a cable-stayed road bridge linking Pyeongtaek and Dangjin over the West Sea. Its total length is 7,310 metres, with a 31.4-metre-wide six-lane deck. Two tall pylons, each made of two columns joined near the top, carry cables fanning down to the deck; their shape copies the Asan Eumnae-dong Dangganjiju, Treasure No. 537.

The Korea Highway Corporation began construction in November 1993 and opened the bridge on 10 November 2000, at a cost of 677.7 billion won. Typhoon Olga damaged the partly built structure on 4 August 1999, when a launching truss and some deck segments fell into the sea without casualties. The bridge carries six lanes on a 31.4 m deck.

The bridge's two pylons were modelled on the stone flagpole supports of Asan Eumnae-dong (Treasure No. 537), a Silla-era pair of uprights. The crossing passes over Haengdamdo, an island being developed with a rest area and hotel as a tourist stop on the West Coast Expressway.

The bridge carries six lanes of the Seohaean Expressway between Pyeongtaek and Dangjin. Sea fog forms over the water on roughly 30 to 50 days a year, and after the 2006 pile-up a section speed-enforcement system was introduced in 2007. The deck crosses Handam Island, where a rest area and hotel stand.

The project faced the challenge of spanning open water with strong maritime winds, requiring specialized engineering to ensure stability. These demanding conditions made it a notable engineering achievement for construction teams.