county, northwestern New York state, U.S., comprising a lowland region that is bordered by Lake Ontario (Ontario, Lake) to the north. It is intersected by the New York State Canal System (and its constituent Erie Canal) and by Oak Orchard Creek. The primary species of tree is oak. Attractions include Lakeside Beach State Park, Oak Orchard State Marine Park, Medina Terminal State Canal Park, and Iroquois National Wildlife Refuge.

county, northern Vermont, U.S., bordered to the north by Quebec, Can., and to the west by the Green Mountains. It consists mostly of a piedmont region that rises in the west to such summits as Jay and North Jay peaks and Belvidere and Haystack mountains. The county contains many waterways, notably Seymour and Caspian lakes, the southern portion of Lake Memphremagog, and the Black, Barton, and Missisquoi rivers. The region, abundant in wildlife, is wooded with spruce, fir, white pine, and maple. Recreational areas include Crystal Lake State Park and Willoughby and Jay Peak state forests.

Orleans county was created in 1792 and probably was named for Louis-Philippe-Joseph, duc d'Orléans (Orléans, Louis-Philippe-Joseph, duc d'). The city of Newport, the county seat, developed as a railroad and logging centre. The Haskell Free Library and Opera House straddles the international border between Derby Line, Vt., and Rock Island, Que.; the players perform on the stage in Canada, while the patrons sit in the auditorium in the United States. Notable landmarks include the Congregational Church (built 1820) in Craftsbury Common and the Old Stone House Museum (built c. 1835) in Brownington. Other communities are Orleans, Barton, North Troy, and Irasburg.

The county's natural resources support tourism, dairy farming, and forest-related industries such as logging, cabinetry, and maple sugar production. Area 697 square miles (1,805 square km). Pop. (2000) 26,277; (2007 est.) 27,302.