Orrtanna is a census-designated place (CDP) in Adams County, Pennsylvania, United States.

[3] Orrtanna was established in 1885 around Orr Station, a stop on the Baltimore and Harrisburg Railway.

The establishment of the post office in 1892 lead to the realization that Orr Glen was already a registered town name in Pennsylvania, so the name finally became Orrtanna in 1892, for Isaiah Orr, a large property owner in the area, and a nearby tannery.

[10] Orrtanna is located in western Adams County at 39°50′53″N 77°21′27″W / 39.84806°N 77.35750°W / 39.84806; -77.35750 (39.848021, -77.357446),[11] at the eastern foot of South Mountain.

According to the United States Census Bureau, the CDP has a total area of 0.19 square miles (0.5 km2), all land.

About 10.6% of families and 19.9% of the population were below the poverty line, including 43.2% of those under the age of eighteen and none of those sixty five or over.

[14] The Gettysburg district's Franklin Township Elementary School has an Orrtanna post office address,[15] but is physically in the Cashtown CDP.