The Seohaean Expressway (Korean: 서해안 고속도로; Seohaean Gosok Doro), meaning "West Coast Expressway", is a freeway in South Korea, connecting Mokpo to Gunsan, Dangjin, and Seoul.

The entire length from Seoul to Mokpo is 345 km and the posted speed limit is 110 km/h, enforced primarily by speed cameras.

It is connected of Seohae Grand Bridge in Pyeongtaek to Dangjin.

Typical facilities of this expressway is Seohae Bridge(Korean: 서해대교; Seohae Daegyo) which the total length of 7.3 km linking the Pyeongtaek(Gyeonggi Province) and Dangjin(Chungnam Province).

346.1 km (215.1 mi) MBC's Entertainment program, Infinite Challenge held a in Haengdam Island Service area in June 2011.