The Tehachapi Loop is a 3,779 feet long spiral, or helix, on the Union Pacific Railroad Mojave Subdivision through Tehachapi Pass, of the Tehachapi Mountains in Kern County, south-central California. The line connects Bakersfield and the San Joaquin Valley to Mojave in the Mojave Desert.
Rising at a steady two percent grade, the track gains 77 feet in elevation making a 1,210-foot diameter circle in the Loop. Any train at least as long as the loop passes over itself going around the loop. At the bottom of the loop, the track passes through Tunnel 9, the ninth tunnel built as the railroad worked from Bakersfield.