- Yellowstone National Park is the first and oldest national park in the United States.
- Yogo sapphire is the state gemstone of Montana. It is found only in Yogo Gulch, near Lewistown.
- The Yaak River is a major tributary of the Kootenai River. It flows through the Yaak Valley in northwestern Montana.
- Yellowstone Cutthroat Trout is the state fish of Montana. It is found only in the Yellowstone River and its tributaries.
- Yale Mountain is the highest point in the Bitterroot Range. It is located in Ravalli County, Montana.
