Two new species of Lasianthus (Rubiaceae), L. thuyanae V.S. Dang & Naiki from Ba Vi National Park, Ha Noi City, northern Vietnam, and L. tamdaoensis V.S. Dang from Tam Dao National Park, Vinh Phuc Province, northern Vietnam, are described and illustrated. Lasianthus thuyanae is closely related to L. curtisii but differs from it by having larger stipules and corollas, and a differently coloured calyx. Lasianthus tamdaoensis resembles L. filipes and L. longipedunculatus but differs from them by having longer petioles and larger corolla lobes.