Trillium oostingii, also known as Wateree trillium, is a wildflower with a limited range, endemic to the central part of the US State of South Carolina. Wateree trillium grows under a canopy of deciduous trees such as bitternut hickory, black walnut, slippery elm, box-elder, and various oak species, in rich floodplain soils. Here it forms large colonies alongside mayapple, another spring-flowering herb. Wateree trillium has three broadly rounded, mottled leaves atop a single, 10–30 cm stem. Its flowers have three green-yellow petals and three green to maroon sepals.