K-15 is a Kansas state highway originating at the Oklahoma state line and continuing to the Nebraska state line where it is then signed as Nebraska Highway 15. It is signed as State Highway 18 once the highway enters Oklahoma. It is 206 miles (332 km) long. Throughout Kansas, it is signed as the Eisenhower Memorial Highway due to its route through Abilene, where the Eisenhower Memorial Museum and Library is located.

From the Oklahoma state line, K-15 runs north for 8 miles (13 km) before turning west for 4 miles (6.4 km) and overlapping US-166. It then returns to a due north course for 9 miles (14 km) to Dexter. Then, it heads west for 3 miles (4.8 km) where it again overlaps, this time with US-160.

At Winfield, K-15 follows US-77 west to Udall and then turns north then cuts through Mulvane. It then continues traveling north through Derby, finally joining I-135 and US-81 in Wichita. K-15 is a multilane divided highway beginning immediately southeast of Mulvane at its intersection with K-53. K-15 follows this four-lane alignment through both Mulvane and Derby until merging with I-135 in south Wichita.

K-15 follows the I-135 alignment to US-50, where it exits after less than a mile onto Kansas Avenue (old US-81) in Newton. It goes through Newton and North Newton then continues north to US-56 in Marion County. It meets K-215 near Goessel. It overlaps US-56 east for 6 miles (9.7 km) then continues north through Durham before crossing K-4. It keeps heading towards Abilene, where it crosses I-70, and continues north to K-18.

K-15 overlaps K-18 another 4 miles (6.4 km) before returning north and crossing US-24 at Clay Center. K-9 joins K-15 for 12 miles (19 km), then departs. K-15 overlaps US-36 for 6 miles (9.7 km) before returning north to end the Nebraska border, becoming N-15.

K-15 once split into two routes near Washington. The K-15W fork is the present-day routing of K-15, while K-15E was redesignated as part of K-148. K-15 was the only state route in Kansas to fork in this manner.

These highways are short spurs from K-15.