Trifolium thompsonii is a species of flowering plant in the legume family known by the common name Thompson's clover. It is endemic to Washington State in the United States, where it occurs in two counties. One of the largest populations occurs in the Entiat Slopes Natural Area Preserve in Chelan County. A Research Natural Area, the Thompson Clover Research Natural Area, was established in 1977 in the Wenatchee National Forest for the study and protection of this species.