Stillwater is a borough in Columbia County, Pennsylvania, United States.

Fishing Creek, a tributary of the Susquehanna River, runs southward through Stillwater.

Stillwater is flat in the middle, with rolling hills in the east and west.

Of all households, 27.1% were made up of individuals, and 14.1% had someone living alone who was 65 years of age or older.

None of the families and 3.3% of the population were living below the poverty line, including no under eighteens and 4.8% of those over 64.

The main character of the CBS show NCIS, Leroy Jethro Gibbs, comes from Stillwater.

The sixth-season episode "Heartland" takes place in Stillwater as Gibbs is forced to return to his hometown to solve a case, and also confront his estranged father.