Northern Territory Spermacoce are revised, with 53 native species recognised, as well as four introduced species. Thirty-nine new species are described, and S. laevigata var. hispida Benth. is raised to species level. Lectotypes are chosen for all Australian Spermacoce names that had any ambiguity regarding types. Key features used to distinguish species, such as the appendages that occur on the inside of the corolla lobes and various seed characteristics, are illustrated and discussed. A key to all the Spermacoce species occurring in the Northern Territory is provided, along with distribution maps.