Valencia is a borough in Butler County, Pennsylvania, United States. The original name of the town was Sunnyside, but was changed for the railroad due to an existing stop with the same name in Lancaster, Pa. It is unknown how the name Valencia was chosen. The population was 551 at the 2010 census.
Valencia is located along the southern border of Butler County at 40°40′30″N 79°59′19″W (40.674906, -79.988493), in the valley of Breakneck Creek near its source. It is bordered to the north, east, and west by Adams Township and to the south by Richland and Pine townships in Allegheny County.
According to the United States Census Bureau, Valencia has a total area of 0.34 square miles (0.87 km2), all of it land.
As of the census of 2000, there were 384 people, 100 households, and 75 families residing in the borough. The population density was 996.2 people per square mile (380.2/km²). There were 106 housing units at an average density of 275.0 per square mile (104.9/km²). The racial makeup of the borough was 98.18% White, 0.52% African American, 0.78% Pacific Islander, and 0.52% from two or more races.
There were 100 households, out of which 35.0% had children under the age of 18 living with them, 57.0% were married couples living together, 13.0% had a female householder with no husband present, and 25.0% were non-families.