Butler County is a county located in the U.S. state of Pennsylvania. As of the 2010 census, the population was 183,862. Its county seat is Butler.[2] Butler County was created on March 12, 1800, from part of Allegheny County and named in honor of General Richard Butler, a hero of the American Revolution.

Butler County is included in the Pittsburgh, PA Metropolitan Statistical Area.

Some famous inventions and discoveries were made in Butler County. It was in Saxonburg, that the designer of the Brooklyn Bridge, John Roebling, invented his revolutionary "wire rope." At what is now known as Oil Creek, Butler County resident William Smith and Edwin Drake first proved that oil could be tapped from underground for consistent supply. The Jeep was developed in Butler County by American Bantam in 1941.

Famous politicians have lived in and traveled through Butler County. George Washington passed through during the French and Indian War. Butler's only U.S. Senator, Walter Lowrie, built a home in 1828 that still stands behind the Butler County Courthouse. The Butler County Historical Society's office is located in this home. Butler's highest ranked federal official ever is William J. Perry, Secretary of Defense under President Bill Clinton from 1994-1997. He graduated from Butler High School in 1945. In 1923, President Warren G. Harding's funeral train passed through Butler County on its way back to Washington D.C. John F. Kennedy delivered a speech in front of the Butler County Courthouse during the United States presidential election, 1960. Hubert Humphrey also spoke in Butler during this time period. Then in 2004, Vice President Dick Cheney delivered a speech in Saxonburg to rally support for President George W. Bush during the United States presidential election, 2004. Bret Michaels, lead singer of the rock band Poison was also born here in 1963.