Kentucky Route 91 (KY 91) is a 49.783-mile-long (80.118 km) state highway that traverses three counties in western Kentucky. It begins in Hopkinsville, Kentucky and ends at the Ohio River, the Kentucky-Illinois state line in northern Crittenden County.

It begins at a junction with U.S. Route 68 and Kentucky Route 80 in Hopkinsville, Kentucky, the Christian County seat. It crosses KY-1682, the Hopkinsville By-Pass before leaving town. It goes on a northwesterly path, and its junction with Kentucky Route 398 is KY 91's access point to Pennyrile Forest State Resort Park.^[2]

KY 91 enters Caldwell County, and then it would meet Kentucky Routes 139 and 293, along with US 62 in downtown Princeton. It then traverses Interstate 69 on the northwest outskirts of Princeton.^[3][4]

KY 91 meets Kentucky Route 70 and then U.S. Route 641 at Fredonia, a community northwest of Princeton. KY 70, KY 91, and US 641 then run concurrently from there into Crittenden County. KY 70 departs from US 641/KY 91 at a point north of the Crittenden-Caldwell County line, while KY 91 remains with US 641 until the U.S. Route's northern terminus at the U.S. Route 60 junction at Kentucky. For a few blocks, KY 91 runs concurrently with US 60, and then KY 91 goes further north to reach its northern terminus at the Cave-In-Rock Ferry on the Ohio River, which also marks the Kentucky-Illinois state line. It becomes Illinois State Highway 1 upon entry into Hardin County, Illinois.^[3][5]

County	Location	mi[1]	km	Destinations	Notes
Christian	Hopkinsville	0.000	0.000	US 68 (Cadiz Road) / KY 80 (West 7th Street)	Southern terminus of KY 91
		0.679	1.093	KY 1682 (Eagle Way) to I-169
	Sinking Fork	5.43	8.74	KY 1349 south (Quisenberry Lane)	Northern terminus of KY-1349
	Sinking Fork	6.351	10.221	KY 1026 west (Gracey-Sinking Fork Road)	Southern end of KY 1026 concurrency
	Sinking Fork	6.718	10.812	KY 1026 east (Clark Store-Sinking Fork Road)	Northern end of KY 1026 concurrency
	Bainbridge	11.709	18.844	KY 398 north (Bainbridge Road) – Pennyrile Forest State Resort Park	Southern terminus of KY 398
	Bainbridge	12.231	19.684	KY 124 west (Sugar Creek Road)	Eastern terminius of KY 124
Caldwell	​	17.562	28.263	KY 672
	​	22.09	35.55	KY 1857 south (Dripping Spring Road)	Northern terminus of KY 1857
	​	22.948	36.931	KY 1603 north (Scottsburg Road)	Southern terminus of KY 1603
	​	24.043	38.693	KY 128 south (State Route 128)	Northern terminus of KY 128
	Princeton	26.736	43.027	KY 2080 south (Cadiz Street)	Northern terminus of KY 2080; old KY 139
		26.839	43.193	East Main St./East Washington St.	Begin splitting of KY 91’s south/north lanes
		26.981	43.422	US 62 West (Do Not Enter)	Eastern end of concurrency with US 62 eastbound/KY 139 northbound
		26.999	43.451	US 62 east / KY 293 north	Northern end of US 62 east/KY-293 north concurrency; eastern end of concurrency with US 62 westbound/KY 293 southbound
		27.017	43.480	KY 139 south / KY 293 south	Southern end of KY 139 concurrency; western end of KY 293 southbound concurrency
		27.305	43.943	US 62 east / KY 91 south / KY 139 south	End splitting of KY 91’s south/north lanes
		28.05	45.14	US 62 west – Eddyville	Western end of US 62 concurrency
		28.493– 28.553	45.855– 45.952	I-69 – Paducah, Elizabethtown	I-69 Exit 79; Former Western Kentucky Parkway exit 11
	​	30.106	48.451	KY 139 north (Farmersville Road)	Northern end of KY 139 concurrency
	Fredonia	39.59	63.71	KY 70 east – Madisonville	Southern end of KY 70 concurrency
		40.082	64.506	US 641 south – Eddyville	Southern end of US 641 concurrency
see US 641 or KY 70
Crittenden	Marion	49.328	79.386	US 60 west (West Gum Street) – Paducah	Northern terminus of US 641 and northern end of US 641 concurrency; southern end of concurrency with US 60
see US 60
Crittenden	Marion	49.625	79.864	US 60 east – Morganfield	Northern end of US 60 concurrency
		50.072	80.583	KY 981 south (Old Salem Road)	Northern terminus of KY 981
	​	58.018	93.371	KY 387 north	Southern terminus of KY 387
	​	59.548	95.833	KY 135 south – Carrsville	Northern terminus of KY 135
Ohio River		60.887	97.988	Cave-In-Rock Ferry; Kentucky-Illinois state line
				IL 1	Continuation into Illinois
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus