K-3 is a 43.262-mile-long (69.623 km) state highway in southeastern Kansas that runs through Crawford, Bourbon and Linn counties from K-47 near Girard to K-31 near Blue Mound.

K-3 begins at an intersection with K-47 west of Girard in Crawford County and heads north on a two-lane road through plains.

Approximately three miles (4.8 km) north of its southern terminus, the route passes through the small community of Brazilton.

Shortly after, the highway leaves K-39 and turns to the north, continuing in that direction for about seven miles (11 km) before bending to the northwest.

The highways curve to the northwest, running through slightly wooded flat lands.