Big Oak Tree State Park is a state-owned nature preserve with recreational features encompassing 1,029 acres (416 ha) in East Prairie, Missouri, United States. The state park was established in a large expanse of drained cropland in 1938 to protect some of the largest trees in the state and in the nation. The park was declared a National Natural Landmark in May 1986, recognized as a rare, untouched wet-mesicbottomland hardwood forest in the Mississippi Alluvial Plain portion of the Gulf Coastal Plain.
Big Oak Tree State Park is the home of many current and past state and national champion trees—trees that are, for their species, the largest in the state or in the nation.
The park has two trails for hiking through the forest, including an accessible boardwalk trail, plus an interpretive center along the boardwalk and picnicking facilities.