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 former right-of-way of the 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" (crushed limestone).
The nickname "Katy" comes from the phonetic pronunciation of "KT", a short form of the railroad's abbreviated name, MKT. Sections of the Katy are also part of the Lewis and Clark National Historic Trail and the American Discovery Trail.