The City of Rocks National Reserve, also known as the Silent City of Rocks, is a National Reserve and state park in United States lying 2 miles (3.2 km) north of the south central Idaho border of Utah. It is widely known for its excellent rock climbing and rock formations.

The rock spires in the City of Rocks and adjacent Castle Rocks State Park are largely composed of rocks of granite of Oligocene Almo pluton and Archean Green Creek Complex.

The City of Rocks is a popular rock climbing area, with numerous traditional and bolt-protected routes. In the 1980s, it was home to some of the most difficult routes in the USA, mostly developed by Idaho climber Tony Yaniro. Climbers in the region refer to the area as simply 'The City'.