Auburn is a city in and the county seat of Androscoggin County, Maine, United States. The population was 23,055 at the 2010 census. It is one of two principal cities of and included in the Lewiston-Auburn, Maine metropolitan New England city and town area and the Lewiston-Auburn, Maine Metropolitan Statistical Area (which is part of the Portland-Lewiston-South Portland, Maine combined statistical area). Auburn and Lewiston (directly across the Androscoggin River) are known as the Twin Cities.