The Cajon Pass (elevation 4,190 ft/1,277 m) is a mountain pass crossing the San Bernardino Mountains in Southern California in the United States. It was created by the movements of the San Andreas Fault. The pass provides an important economic link from the Los Angeles Basin to Victor Valley and the Mojave Desert.

In 1851, a band of Mormon settlers led by Amasa Lymand and Charles Rich crossed the Cajon Pass on their way from Salt Lake City to the Los Angeles basin. In commemoration of this crossing, a section of the pass where the railroad passes through (near Sullivan's Curve ) is now known as Mormon Rocks.

The Santa Fe Railway was the first railroad to use the Cajon Pass as a route into the Los Angeles area. Today, the Union Pacific Railroad and BNSF Railway (the successor to the Santa Fe) use this pass. Due to the high volume of trains and easy access, it is a popular railfanning location.

The Mojave Freeway (Interstate 15) was built over the Cajon Pass and provides a major route from Los Angeles to Las Vegas.