Penbrook is a borough in Dauphin County, Pennsylvania, United States, founded in 1861 and incorporated July 10, 1894. Penbrook was once named East Harrisburg and still maintains a Harrisburg postal ZIP code. The population was 3,268 at the 2020 census.

Dauphin County is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 286,401. The county seat is Harrisburg, Pennsylvania's state capital and ninth-most populous city. The county was created on March 4, 1785, from part of Lancaster County and was named after Louis Joseph, Dauphin of France, the first son of King Louis XVI. The county is part of the South Central Pennsylvania region of the state.