Oxford County is a county in the state of Maine, United States. As of the 2020 Census, the county had a population of 57,777. Its county seat is the town of Paris. The county was formed on March 4, 1805, by the Massachusetts General Court in the Maine District from northerly portions of York and Cumberland counties. It borders the Canadian province of Quebec. Part of Oxford County is included in the Lewiston-Auburn, Maine metropolitan New England City and Town Area while a different part of Oxford County is included in the Portland-South Portland-Biddeford, Maine metropolitan New England City and Town Area.

Cumberland County is a county in the U.S. state of Maine. As of the 2020 census, the population was 303,069, making it the most populous county in Maine. Its county seat is Portland. Cumberland County was founded in 1760 from a portion of York County, Province of Massachusetts Bay, and named for William, Duke of Cumberland, a son of King George II. Cumberland County has the deepest and second-largest body of water in the state, Sebago Lake, which supplies tap water to most of the county. The county is the state's economic and industrial center, having the resources of the Port of Portland, the Maine Mall, and having corporate headquarters of major companies such as Fairchild Semiconductor, IDEXX Laboratories, Unum, and TD Bank. Cumberland County is part of the Portland–South Portland, ME Metropolitan Statistical Area.