The reduviid genus Sinea presently is represented in America north of Mexico by 10 species, one of which is Sinea complexa Caudell. This species has been listed from California east to Missouri and Illinois. In fact, it does not occur in Missouri and Illinois but is limited primarily to the West and Southwest. A new species, Sinea incognita McPherson, described herein, occurs from Maryland south to Georgia and west to Kansas and Texas. It closely resembles S. complexa, for which we provide distinguishing characters; J.E.M. designates a male lectotype and female paralectotype for Caudell’s syntypes. A third species, Sinea integra Stål, currently known only from Mexico, shares with S. incognita and S. complexa the presence of spines and tubercles on both lobes of the pronotum rather than just on the anterior lobe as is typical of other Sinea spp. Because we discuss the three species in this article, and Stål did not designate a holotype for either of his two syntypes of S. integra (a male and female) deposited in the Swedish Museum of Natural History, J.E.M. also designates a male lectotype and female paralectotype for this species.