| State: | UT |
| Type: | SR |
| Route: | 123 |
| Section: | 118 |
| Map Custom: | yes |
| Map Notes: | SR-123 highlighted in red |
| Length Mi: | 11.421 |
| Length Round: | 3 |
| Length Ref: | [1] |
| Established: | 1931[2] (as SR-124, renumbered in 1933) |
| Direction A: | West |
| Terminus A: | at Sunnyside Junction |
| Junction: | in East Carbon |
| Direction B: | East |
| Terminus B: | Whitemore Canyon Road in East Carbon |
| Previous Type: | SR |
| Previous Route: | 122 |
| Next Type: | SR |
| Next Route: | 124 |
Utah State Route 123 (SR-123) is a state highway in the U.S. state of Utah. Spanning 11.4miles, it connects the city of East Carbon with US-6 / US-191 in Carbon County.
State Route 123 begins at Sunnyside Junction on US-6/US-191, about 15miles southeast of Price. It heads east, passing through East Carbon-Sunnyside at the base of the Book Cliffs. It turns to the northeast and terminates shortly after it enters Whitmore Canyon.
The road from Sunnyside Junction through Sunnyside to Columbia (now all part of East Carbon-Sunnyside) was added to the state highway system in 1931, initially numbered SR-124[3] but changed to SR-123 in 1933.[4] The route was shortened in 1935 by moving the eastern terminus back into Sunnyside,[5] and splitting off the portion from Sunnyside to Columbia as SR-124.[6]