The Santa Margarita River which with the addition of what is now Temecula Creek, was formerly known as the Temecula River, is a short intermittent river on the Pacific coast of southern California in the United States, approximately 30.9 miles (49.7 km) long. One of the last free-flowing rivers in southern California, it drains an arid region at the southern end of the Santa Ana Mountains, in the Peninsular Ranges between Los Angeles and San Diego.

The Santa Ana Mountains are a short peninsular mountain range along the coast of Southern California in the United States. They extend for approximately 61 miles (98 km) southeast of the Los Angeles Basin largely along the border between Orange and Riverside counties.