Marsing is a city in Owyhee County, Idaho, United States. The population was 890 at the 2000 census. It is part of the Boise City–Nampa, Idaho Metropolitan Statistical Area.
Marsing is located at 43°32′44″N 116°48′28″W / 43.54556°N 116.80778°W / 43.54556; -116.80778 (43.545484, -116.807811).
According to the United States Census Bureau, the city has a total area of 0.7 square miles (1.7 km²), all of it land.