Orrington is a town on the Penobscot River estuary in Penobscot County, Maine, United States. The population was 3,733 at the 2010 census.
Orrington was originally part of Condustiegg (or Kenduskeag) Plantation, which also included the present-day cities of Bangor and Brewer. Orrington was incorporated as a town in 1788 with its major village at Brewer, then called "New Worcester". Bangor incorporated three years later in 1791. Brewer broke away from Orrington in 1812 to form a separate town.
The name "Orrington" reportedly resulted from a spelling mistake. The settlers intended to name it "Orangetown" after Orangetown, Maryland, but it was written on the record-books in distant Massachusetts, of which Maine was then a territory, as "Orrington". "Orring" was a reasonable phonetic rendering of "orange" before the standardization of English spelling.
According to the United States Census Bureau, the town has a total area of 27.33 square miles (70.78 km2), of which, 24.99 square miles (64.72 km2) of it is land and 2.34 square miles (6.06 km2) is water.
As of the census of 2010, there were 3,733 people, 1,478 households, and 1,068 families living in the town. The population density was 149.4 inhabitants per square mile (57.7/km2). There were 1,612 housing units at an average density of 64.5 per square mile (24.9/km2).