State Route 117 (SR 117) is an east–west highway in the western part of the U.S. state of Ohio. Its western terminus is at State Route 118 near Rockford, and its eastern terminus is at U.S. Route 33 near Huntsville. It goes through the towns of Spencerville and Lima, and comes close to Indian Lake. East of Lima, the route takes a southeast to south-southeast heading to its eastern terminus.

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State Route 117 was an original state highway that went from State Route 116 a few miles east of Spencerville to Bellefontaine, with the portion from Huntsville to Bellefontaine a concurrency with then State Route 32.

In 1926, rerouting switched State Route 116 and State Route 198 so that the former would have a straighter heading. State Route 198 was given State Route 116's former heading into Wapakoneta and was truncated at route State Route 117's then-western terminus, and State Route 117 was extended on State Route 116's former eastern heading through Spencerville and all the way to then-State Route 9 (now U.S. Route 127) through Mendon. In the same year, its concurrency with State Route 32 was ended, and its eastern terminus was moved to Huntsville.

In 1938, another rerouting moved State Route 117's western terminus to its current terminus. Its route through Mendon was recertified as State Route 707.

In 1950, State Route 117 was once again routed in a concurrency to Bellefontaine, this time with U.S. Route 33 (which had replaced State Route 32 in 1938). This concurrency was ended in 1968, and State Route 117 was truncated at its current eastern terminus.

County	Location	mi	km	Destinations	Notes
Mercer	Dublin Township	0.00	0.00	SR 118
		4.11	6.61	US 127 – Van Wert, Celina
	Union Township	7.64	12.30	SR 707 west / CR 151C (Hickernell Road) – Mendon	Eastern terminus of SR 707
Van Wert	Jennings Township	12.56	20.21	SR 116 south / Louth Road – St. Marys	Western end of SR 116 concurrency
		12.76	20.54	SR 116 north / Biner Road – Van Wert	Eastern end of SR 116 concurrency
Allen	Spencerville	16.54	26.62	SR 66 (North Broadway Street)
	Amanda Township	20.40	32.83	SR 198 south / CR 71 (South Conant Road) – Wapakoneta	Northern terminus of SR 198
	Shawnee Township	24.54	39.49	SR 501 south / Wapak Road	Northern terminus of SR 501
	Lima	30.64	49.31	SR 65 north / SR 309 west (South Union Street)	Western end of SR 65 / SR 309 concurrencies
		30.85	49.65	SR 65 south (South Pine Street)	Eastern end of SR 65 concurrency
		32.19– 32.38	51.80– 52.11	I-75 – Dayton, Findlay, Toledo	Exit 125 (I-75)
	Bath–Perry township line	32.51	52.32	SR 309 east / Willard Avenue – Kenton	Eastern end of SR 309 concurrency
	Auglaize Township	38.47	61.91	SR 196 south – Waynesfield	Northern terminus of SR 196
Auglaize–Hardin county line	Wayne–Roundhead township line	46.28	74.48	SR 67 west – Wapakoneta	Western end of SR 67 concurrency
Hardin	Roundhead Township	47.86	77.02	SR 67 east / TR 170 – Kenton	Eastern end of SR 67 concurrency
		50.09	80.61	SR 385 west / East Mill Street	Eastern terminus of SR 385
		50.22	80.82	SR 235 north – Ada	Western end of SR 235 concurrency
		52.17	83.96	SR 235 south	Eastern end of SR 235 concurrency
Logan	Richland Township	53.13	85.50	SR 273 west – Long Island	Western end of SR 273 concurrency
		53.96	86.84	SR 273 east – Mount Victory	Eastern end of SR 273 concurrency
	Richland–McArthur township line	56.98– 57.23	91.70– 92.10	SR 366 north – Russells Point, Lakeview	Southern terminus of SR 366
	McArthur Township–Huntsville municipal line	58.25	93.74	SR 274 west	Western end of SR 274 concurrency
	McArthur Township	58.95	94.87	SR 274 east / Sharon Street	Eastern end of SR 274 concurrency
		59.06– 59.57	95.05– 95.87	US 33 / CR 130 – Russells Point, Bellefontaine, Marysville	Interchange
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus