State Route 126 (SR-126) is a highway completely within the Ogden-Clearfield metropolitan area in northern Utah that makes a loop around Interstate 15 in its more than twenty-one mile path. The street is given the names Main Street, 1900 West and 2000 West respectively from south to north. Previous to 1977, SR-126 was a road in southern Utah. A portion of the highway is an old routing of US-91.

After its southern terminus, the route heads northwest in Layton. After entering Clearfield, the route turns straight to the north. It continues this direction through Sunset, Roy, and West Haven before veering to the northwest when the highway reaches Marriott-Slaterville. The route again reverts to a northerly direction before reaching Farr West. Just before terminating in South Willard, the route turns northeast one final time.

The entirety of the route, with the exception of a small portion from the Interstate 15/Interstate 84 junction to the northern terminus, lies west of the aforementioned interstates.

The portion of what is now numbered SR-126 from the southern terminus to the junction with SR-26 was previously part of US-91. The northern portion of what is now SR-126 was numbered State Route 84 starting in 1953. In 1974, US-91 was eliminated throughout most of Utah, and SR-84 absorbed the portion of former US-91 from Layton to Roy.

The 1977 Utah state route renumbering was implemented, in part, to eliminate instances where a state route used the same number as a U.S. Route or Interstate route in the state. As the 84 designation was also in use for Interstate 84 most of SR-84 was renumbered to SR-126. The only change from then to now was a portion of the old highway that was relinquished to be used by the city of Layton for parking lots in 1991.

County	Location	mi	km	Destinations	Notes
Davis	Layton	0.000	0.000	Fort Lane	Southern terminus
		0.111– 0.200	0.179– 0.322	I-15 – Salt Lake City, Ogden	I-15 exit 330
		0.624	1.004	SR-109 east (Gentile Street)	Western Terminus of SR-109
		1.700	2.736	SR-232 east (Hill Field Road)
		3.320	5.343	SR-108 (Antelope Drive) – Antelope Island
	Clearfield	4.557	7.334	SR-193 east (700 South)
		7.741	12.458	300 North	Former SR-107
		6.084	9.791	SR-103 east (650 North) to I-15
	Sunset	7.237	11.647	SR-37 west (1800 North)	Southern Terminus of SR-37
Weber	Roy	8.738	14.062	SR-97 (5600 South)
		9.126	14.687	SR-26 east (Riverdale Road) to I-15 / I-84	Western Terminus of SR-26
		11.247	18.100	SR-79 east (Hinckley Drive)	Western Terminus of SR-79
		11.743	18.899	SR-108 west (Midland Drive)	Northern Terminus of SR-108
	West Haven	13.344	21.475	SR-104 east (Wilson Lane)
	Marriott-Slaterville	14.459	23.270	SR-39 (12th Street)
	Farr West	18.721	30.129	SR-134 (2700 North)
Box Elder	South Willard	21.011– 21.264	33.814– 34.221	I-15 / I-84 – Salt Lake City, Brigham City	I-15 exit 351
	Hot Springs Junction	21.506	34.611	US 89 – Brigham City, Logan	Northern terminus
1.000 mi = 1.609 km; 1.000 km = 0.621 mi