| Chamaesyce salsuginosa McVaugh, 1995 |
| Chamaesyce scopulorum (Brandegee) Millsp., 1914 |
| Chamaesyce scopulorum var. inornata (M.C. Johnst.) V.S. Raju & P.N. Rao, 1978 |
| Chamaesyce scopulorum var. nuda (M.C. Johnst.) V.S. Raju & P.N. Rao, 1978 |
| Chamaesyce seleri (Donn. Sm.) Millsp., 1916 |
| Chamaesyce serpens (Kunth) Small, 1903 |
| Chamaesyce serpyllifolia (Pers.) Small, 1903 |
| Chamaesyce serpyllifolia subsp. hirtula (Engelm. ex S. Watson) Koutnik, 1985 |
| Chamaesyce serrula (Engelm.) Wooton & Standl., 1913 |
| Chamaesyce setiloba (Engelm. ex Torr.) Millsp. ex Parish, 1913 |
| Chamaesyce simulans (L.C. Wheeler) Mayfield, 1993 |
| Chamaesyce standleyi Millsp., 1916 |
| Chamaesyce stanfieldii Small, 1903 |
| Chamaesyce stictospora (Engelm.) Small, 1903 |
| Chamaesyce supina (Raf.) Hara, 1940 |
| Chamaesyce tamaulipasana Millsp., 1916 |
| Chamaesyce theriaca (L.C. Wheeler) Shinners, 1949 |
| Chamaesyce theriaca var. spurca (M.C. Johnst.) Mayfield, 1993 |
| Chamaesyce thymifolia (L.) Millsp., 1916 |
| Chamaesyce tomentulosa (S. Watson) Millsp., 1916 |