Gangseo District (Korean: 강서구; RR: Gangseo-gu) is a gu on the west side of Nakdong River in Busan, South Korea. It has an area of 179.05 km2, and a population of about 66,000; it has a lower population density than Gijang County of Busan. Gangseo-gu was part of Buk-gu from its creation in 1978 to 1989 when it became an independent gu.
Gangseo-gu is the westernmost gu in Busan and it shares a common borders with Gimhae on its north-west side and Jinhae District, Changwon on its south-west side.