The Moira River flows from its source near Sharbot Lake in eastern Ontario to empty into the Bay of Quinte on Lake Ontario at Belleville, Ontario. The river is 98 km in length.
The Skootamatta River, Clare River and Black River are tributaries of this river which join the Moira near Tweed, Ontario. South of the town of Madoc, the river widens into Moira Lake, a popular recreational lake.
The river was named after Francis Rawdon-Hastings, Earl of Moira.