State Route 18 (SR 18) is a state highway in the U.S. state of California. It serves as a primary route into the San Bernardino Mountains, both from the Riverside–San Bernardino metropolitan area from the south and the Mojave Desert from the north. SR 18 runs from State Route 210 in San Bernardino to State Route 138 in Llano. It has two discontinuities: one in Big Bear Lake, the other in Victorville.