| Rainbow Basin Natural Area | |
|---|---|
 The famous Rainbow Basin syncline | |
  Map of California  Rainbow Basin (the United States) | |
| Location | San Bernardino County, California |
| Nearest city | Barstow |
| Coordinates | 35°01′46″N 117°02′12″W / 35.02944°N 117.03667°W |
| Area | 1,961 acres (794 ha) |
| Designated | 1966 |
Rainbow Basin is a geological formation in the Calico Peaks range, located approximately 8 miles (13 km) north of Barstow in the Mojave Desert in San Bernardino County, California.
The Rainbow Basin has been designated a National Natural Landmark and is in the Bureau of Land Management managed Rainbow Basin Natural Area. Rainbow Basin is a mixture of private and public land, but it is managed by the Bureau of Land Management. It is accessible to the public via Irwin Road from Barstow to an unpaved loop road through the colorful basin.
The basin is notable for the fantastic and beautiful[peacock prose] shapes of its rock formations as well as its fossil beds, which have provided scientists with valuable information about life during the middle Miocene epoch, between 12 and 16 million years ago; and to the northeast the Calico Early Man Site.