U.S. Route 399 was a U.S. Highway that ran from Ventura, California to Bakersfield, California. It was established in 1934 and deleted in 1964, as it was only 137 miles (219 km) long, less than the minimum 300 miles (480 km) that AASHTO set as the threshold for U.S. Highways. It has been replaced with a segment of State Route 33, all of State Route 119, and a segment of State Route 99.