From List of National Natural Landmarks, these are the National Natural Landmarks in Oklahoma. There are 3 in total.
||Known for several different mesic plants in a diverse environment of oak woodland/tall prairie grass and eastern deciduous forest
||McCurtain County Wilderness Area
||Broken Bow 34°16′55″N 94°41′48″W / 34.281971°N 94.696655°W
||A 14,087 acres (57.01 km2) wilderness nature preserve since 1918. It is an excellent example of a xeric upland oak-pine forest
||Salt Plains National Wildlife Refuge
||Jet 36°45′01″N 98°13′27″W / 36.750314°N 98.224259°W
||A 32,000-acre (130 km2) National Wildlife Refuge, it is a critical habitat for 75% of the endangered whooping crane population.