U.S. Route 310 (US 310) is a spur of historic U.S. Route 10, now Interstate 90. It runs for 108 miles (174 km) from Laurel, Montana, to Greybull, Wyoming. It passes through the states of Montana and Wyoming. Near the town of Lovell, Wyoming, US 310 is concurrent with US 14A for approximately 3 miles (4.8 km).

US 310 starts at a junction with US 14, US 16, and US 20 west of Greybull; Highway 789 continues north along US 310 through the desert. Near the town of Lovell, US 310 passes by Lovell Lakes before turning west through a brief stretch of farmland that extends into Cowley. From Cowley, the highway runs west to Deaver, then due north to Frannie, where it straddles the boundary between Big Horn County and Park County. Just to the north of Frannie, US 310 bends slightly to the west, so that the road is actually inside Park County by about 400 feet before reaching the Montana state line. At the state line, Wyoming Highway 789 ends and US 310 continues northwest into the desert. At the junction with Montana Highway 72, US 310 turns north, passing through farmland and the towns of Bridger and Fromberg before running concurrently with US 212. The highway enters the city of Laurel, where US 212 continues onto I-90, and US 310 ends at Main Street.

Historically, US 310 intersected with US 10 at Laurel. After 1986, when US 10 was decommissioned west of West Fargo, North Dakota, US 310 no longer connected to its "parent" route.

State	County	Location	mi	km	Destinations	Notes
Wyoming	Big Horn	Greybull	0.00	0.00	US 14 / US 16 / US 20 / WYO 789 south – Greybull, Cody, Yellowstone	South end of WYO 789 overlap
		Lovell	27.03	43.50	US 14A east – Burgess Junction	South end of US 14A overlap
			28.77	46.30	WYO 32 – Emblem
		​	30.23	48.65	US 14A west – Byron, Powell, Cody	North end of US 14A overlap
		Cowley	34.16	54.98	WYO 35 / CR R7
		Deaver	40.14	64.60	WYO 114 – Garland, Powell, Cody
	Park	No major junctions
			47.93 0.000	77.14 0.000	Wyoming–Montana state line; WYO 789 ends
Montana	Carbon	Bridger	24.700	39.751	MT 72 – Belfry, Cody
		Rockvale	42.628	68.603	US 212 west – Red Lodge	South end of US 212 overlap
	Yellowstone	Laurel	54.154	87.152	I-90 / US 212 east – Billings, Butte	North end of US 212 overlap
			54.646	87.944	I-90 BL (Main Street) / S-532
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus

• Endpoints of U.S. Highway 310

Browse numbered routes
← MT 287	MT	→ US 312
← WYO 296	WY	→ WYO 310