Chamaesyce skottsbergii)[1] is a rare species of flowering plant in the euphorb family known by the common names coastal sandmat and Skottsberg's broomspurge.

It is endemic to Hawaii, where it is found in coastal shrublands[2] on Oʻahu, Molokaʻi, Maui, and Kahoʻolawe.

It had been reduced in population by a number of factors, including Navy activity, pollution, destruction by bulldozer on private property, quarrying, agriculture, fire, development and construction of housing, roads, an oil refinery, and resort property, and expansion of the harbor.

[3] Other threats include non-native plant species, especially kaunaoa pehu (Cassytha filiformis), kiawe (Prosopis pallida), Chinese violet (Asystasia gangetica), and buffel grass (Cenchrus ciliaris).

[3] Potentially damaging insects that visit the plant include croton moth (Achaea janata) and spiraling whitefly (Aleurodicus dispersus).