State Route 45 (SR-45) is a state highway in the U.S. state of Utah. It runs from Dragon Road south of Bonanza in Uintah County north to US-40 in Naples, south of Vernal. The route spans 40.03 miles (64.42 km) south–north.The route was added to the state highway system in 1925 and numbered in 1927, originally running from US-40 southeast to the Colorado state line. Subsequently, the highway was moved to a new road in 1943, truncated to Bonanza in 1968, and again moved and extended in 1982.