William Findlay was an American farmer, lawyer, and politician. A member of the Democratic-Republican Party, he served as the fourth governor of Pennsylvania from 1817 to 1820, and as a United States senator from 1821 to 1827. He was one of three Findlay brothers born and raised in Mercersburg, Pennsylvania, on their family farm.

Mercersburg is a borough in Franklin County, Pennsylvania, United States. The borough is 72 miles (116 km) southwest of Harrisburg, the state capital.