| Euphorbia chalicophila Weath., 1910 |
| Euphorbia chamaecaula Weath., 1910 |
| Euphorbia chamaepeploides Lotsy, 1895 |
| Euphorbia chamaesula Boiss., 1860 |
| Euphorbia chamaesula var. chamaesula Boiss., 1860 |
| Euphorbia chamaesula var. subdentata (Engelm.) Norton, 1900 |
| Euphorbia chamberlinii I.M. Johnst., 1924 |
| Euphorbia chersonesa Huft, 1984 |
| Euphorbia chiapensis Brandegee, 1914 |
| Euphorbia chiribensis V.W. Steinm. & Felger, 1997 |
| Euphorbia chrysochaeta W. Fitzg., 1918 |
| Euphorbia cinerascens Engelm., 1859 |
| Euphorbia cinerascens var. appendiculata Engelm., 1858 |
| Euphorbia clarionensis Brandegee, 1899 |
| Euphorbia coalcomanensis (Croizat) V.W. Steinm., 2003 |
| Euphorbia cofradiana Brandegee, 1905 |
| Euphorbia colimae Rose, 1895 |
| Euphorbia colletioides Benth., 1846 |
| Euphorbia colligata V.W. Steinm., 2003 |
| Euphorbia collina Brandegee, 1911 |