Analysis of molecular phylogenetic data was used to reveal the existence of a novel species of Trillium subgen. Sessilium. Trillium delicatum sp. nov. differs from the two other low-growing species of the subgenus, T. decumbens and T. reliquum, in features such as straight stems and dung-scented flowers. It occurs in wet floodplain forests in the Oconee and Ocmulgee river drainages in central Georgia, and has a distinct floral scent compared to thewide spectrum in Trillium. The molecular phylogenetic results based on four markers (nuclear ribosomal ITS and plastid trnHpsbA, trnL-trnF, and rpl32-trnL spacers) included samples of all species of the subgenus, and documented the distinctiveness of T. delicatum as a distinct taxon and also provided resolution of species relationships that suggested that the subgenus originated in southeastern North America with twomigrations towestern North America. The molecular results also suggested the need for closer examination of T. cuneatum and T. lancifolium, and also to assess whether T. decipiens and T. underwoodii are distinct species. Based on the few known populations and susceptibility to damage by hogs, Trillium delicatum is a rare species requiring protection.