The Katy Trail State Park is a state park in the U.S. state of Missouri that contains the Katy Trail, the country's longest continuous recreational rail trail. It runs 240 miles (390 km), largely along the northern bank of the Missouri River, in the right-of-way of the former Missouri–Kansas–Texas Railroad. Open year-round from sunrise to sunset, it serves hikers, joggers, and cyclists. Its hard, flat surface is of "limestone pug".

A rail trail is a shared-use path on railway right of way. Rail trails are typically constructed after a railway has been abandoned and the track has been removed but may also share the right of way with active railways, light rail, or streetcars, or with disused track. As shared-use paths, rail trails are primarily for non-motorized traffic including pedestrians, bicycles, horseback riders, skaters, and cross-country skiers, although snowmobiles and ATVs may be allowed. The characteristics of abandoned railways—gentle grades, well-engineered rights of way and structures, and passage through historical areas—lend themselves to rail trails and account for their popularity. Many rail trails are long-distance trails, while some shorter rail trails are known as greenways or linear parks.