Millerstown is a borough in northern Perry County, Pennsylvania, United States, located 29 miles (47 km) northwest of Harrisburg and 29 miles (47 km) southwest of Selinsgrove. The population was 688 at the 2020 Census. The borough is part of the Harrisburg–Carlisle Metropolitan Statistical Area.

Perry County is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 45,842. The county seat is New Bloomfield. The county was created on March 22, 1820, and was named for Oliver Hazard Perry, a hero of the War of 1812, who had recently died. It was originally part of Cumberland County and was created in part because residents did not want to travel over the mountain to Carlisle, the county seat of Cumberland County. Landisburg became the temporary county seat before New Bloomfield was ultimately chosen. The county is part of the South Central Pennsylvania region of the state.