Rochester () is a census-designated place (CDP) in Thurston County, Washington, United States. It was founded in 1852, and the 2010 census recorded its population at 2,388. According to the United States Census Bureau, the CDP has a total area of 2.3 square miles (6.0 square kilometers), all of it land. Rochester Schools had 2095 students registered in 2011.
Rochester was platted in 1890, and named after Rochester, Indiana, the native home of a first settler. An early variant name was "Key".
As of the census of 2000, there were 1,829 people, 647 households, and 505 families residing in the CDP. The population density was 790.2 people per square mile (305.7/km²). There were 677 housing units at an average density of 292.5/sq mi (113.2/km²). The racial makeup of the CDP was 88.41% White, 0.16% African American, 1.69% Native American, 0.93% Asian, 0.11% Pacific Islander, 5.52% from other races, and 3.17% from two or more races. Hispanic or Latino of any race were 10.39% of the population. 12.8% were of German, 11.5% Irish, 7.8% American, 7.5% Norwegian, 5.6% English and 5.4% Scottish ancestry according to Census 2000.