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.