Carex oronensis is a species of sedge known by the common name Orono sedge. It is endemic to Maine in the United States, where it occurs mainly in the Penobscot River Valley. It is the only plant that is endemic to the state of Maine. The type locality is Orono. The Orono sedge produces clumps of stems up to one meter tall. There are three to four leaf blades per stem. Each measures 18 to 23 centimeters long. The copper-colored inflorescence is a few centimeters long and contains several spikes of flowers. Flowering occurs in June and July.