Carbon Glacier, Glacier expanse in Mount Rainier National Park, United States.

Carbon Glacier lies on the north slope of Mount Rainier in Washington and feeds the Carbon River. Its terminus sits at about 3,500 feet (1,100 m), the lowest of any glacier in the contiguous United States. At 5.7 miles (9.2 km) long, 700 feet (210 m) thick and 0.2 cubic miles (0.83 km³) in volume, it is the largest U.S. glacier outside Alaska. Its cirque, over a mile wide, is the largest in the Cascade Range, and its headwall forms the Willis Wall.

Carbon Glacier is fed by the cirque beneath Willis Wall, a headwall over a mile wide that is the largest cirque in the Cascade Mountains. Its terminus sits at about 3,500 feet, the lowest of any glacier in the contiguous United States, and it is the longest, thickest and most voluminous U.S. glacier outside Alaska. The Carbon River rises from its snout.

The Wonderland Trail passes close to the glacier's lower edge, giving hikers a rare chance to stand near active glacial ice. The surface is often covered in dark rock debris, which makes the ice hard to spot at first glance.

Getting to the glacier requires hiking through dense forest and crossing river channels, with noticeable changes in elevation along the way. The ground can be muddy and uneven, so sturdy footwear is a good idea before setting out.

Carbon Glacier is so heavily covered in dark rock debris that from a distance it can look like a plain scree slope with no ice at all. This layer of debris actually insulates the ice from sunlight and slows its melting considerably.