Grass Valley is a city in Sherman County, Oregon, United States.

According to the United States Census Bureau, the city has a total area of 0.51 square miles (1.32 km2), all of it land.

29.7% of all households were made up of individuals, and 20.3% had someone living alone who was 65 years of age or older.

The racial makeup of the city was 95.32% White, 2.34% Native American, 1.17% Asian, and 1.17% from two or more races.

About 6.0% of families and 13.6% of the population were below the poverty line, including 31.0% of those under the age of eighteen and 9.5% of those 65 or over.

Oregon Raceway Park is a 2.3-mile dedicated road course facility just east of the town that hosts competitive automobile, kart and motorcycle events.