Stillwater River may refer to:

• The Stillwater River in Ohio in the United States.
• The Stillwater River, a tributary of the Yellowstone River in southern Montana in the United States.
• The Stillwater River, a tributary of the Whitefish River in western Montana in the United States.
• The Stillwater River in Rhode Island.
• The Stillwater River in Maine.
• The Stillwater River in Massachusetts.
• The Stillwater River in the South Island of New Zealand.