State Route 173 (SR 173) is located in northeastern Ohio, and runs east–west from State Route 44, about 4 miles (6.4 km) north of Louisville, Ohio to State Route 14 and State Route 9 in downtown Salem, Ohio.

SR 173 was commissioned in 1923, originally routed from SR 19. northeast of Louisville, to SR 19, south of Beloit.

[4][5] The route was extended west to its current western terminus, at SR 44, in 1937.

[6][7] Between 1969 and 1971, SR 173 was rerouted concurrent with US 62 from west of Alliance to Salem.

[8][9] In 1976 US 62 in Salem was rerouted to bypass the city and SR 173 remained on the old route of US 62.