K-171 is a state highway in the southeastern part of the U.S. state of Kansas. The 4.9-mile (7.9 km) highway mostly lies on the Crawford County/Cherokee County line except for the easternmost 0.4 miles (0.64 km) of the highway when it is entirely in Cherokee County. Its eastern terminus is at the Missouri state line near Opolis; its western terminus is at the intersection of U.S. Route 69/160 and U.S. Route 400 south of Pittsburg.

K-171 begins at a four-way stop south of Pittsburg. The west arm of this intersection serves as US-400, the north arm carries US-69 and 160, the south arm is US-69, 160, and 400, and the east arm forms the beginning of K-171. From this intersection, the highway heads due east to Opolis. The highway begins to curve to the south just before crossing the state line and becoming Route 171 in Missouri.

The highway is signed with a destination of Joplin, Missouri, due to its connection with Route 171. However, Route 171 only enters Joplin very briefly; it mainly runs through other, smaller cities in the Joplin area.

The eastern K-171 was first designated on July 1, 2003. Prior to K-171's formation, the road was a part of K-57, most of which was decommissioned due to several long concurrencies with other highways.

The K-171 designation was assigned to the highway to match the designation in Missouri; Missouri's Route 171 had been renumbered from Route 57 to resolve a numbering conflict with Interstate 57.

Another K-171 existed in central Kansas and shared the designation with the existing K-171 for several years until it was removed from the state highway system. That K-171 ran from the city of Bushton north to K-4 in northwestern Rice County.