The shrubby, spiny, succulent species Euphorbia collenetteae D.Al-Zahrani & El-Karemy (Euphorbiaceae) from the southern Red Sea coast and islands is described and illustrated as new. Diagnostic characters, a description and taxonomic comments on the species are given. It is compared with the closely related Euphorbia fractiflexa S.Carter & J.R.I.Wood. The geographical distribution of the new species is shown.