Iowa Highway 8 is a state highway that runs from east to west in east central Iowa. Highway 8 is a short state highway in Iowa, at only 14 miles (23 km) long. Iowa 8 begins at an intersection with U.S. Route 63 in Traer and ends at an intersection with U.S. Route 218 northwest of Garrison. The route has largely remained the same since its designation.

Iowa Highway 8 begins in Traer at an intersection with U.S. Route 63. It heads southeast from Traer and then straightens out to the east. Two miles (3.2 km) west of Dysart, Iowa 8 is intersected by Iowa 21. The two highways overlap for two miles until Iowa 21 turns south at Dysart. Iowa 8 continues to the east and ends at a T intersection with U.S. Route 218 northwest of Garrison.

Prior to becoming a primary highway, Iowa Highway 8's route was a part of the Diagonal Trail, which connected Sioux Falls, South Dakota, to Danville, Illinois. Through Iowa, it passed through Davenport, Cedar Rapids, Iowa Falls, Spencer, and Spirit Lake. The Diagonal Trail was registered with the Iowa State Highway Commission on December 4, 1918. When the primary highway system was created, a portion of the Diagonal Trail was assigned Primary Road No. 58. When the eastern portion of Iowa 58 was rerouted, Iowa Highway 8 was formed. Iowa 8 has been relatively unchanged since its designation, with two sharp curves east of Traer eliminated for a straighter route with one more-gradual curve.