Dauphin is a borough in Dauphin County, Pennsylvania, United States. The population was 791 at the 2010 census. Dauphin's ZIP code is 17018. It is part of the Harrisburg–Carlisle Metropolitan Statistical Area.
Dauphin is located on the western edge of Dauphin County at 40°22′00″N 76°55′52″W, on the east bank of the Susquehanna River. The land at the river's edge is alluvial floodplain, but Dauphin sits at the head of a narrow valley between two mountains, at the mouth of Stony Creek. The valley between the two mountains is called Stony Valley, which contains the villages of Singersville and Ellendale Forge. This section along the Susquehanna River is a gateway from the southeastern plains into the Appalachian Mountains and the north-central part of the state. Berrier Island is also located at Dauphin.
Dauphin is surrounded by Middle Paxton Township, which comprises mountains and valleys south of the confluence of the Susquehanna and Juniata rivers. From south to north, the mountains in the township are Blue Mountain, Second Mountain, Third or Stony Mountain, and Peters Mountain.