Spergularia atrosperma is a species of flowering plant in the family Caryophyllaceae known by the common name blackseed sandspurry.

[1] It is native to California and Nevada, where it grows in muddy and sandy habitat, often in moist alkaline substrates.

It is a small annual herb producing a slender stem up to 15 centimeters long.

The inflorescence bears small flowers with five pointed sepals and five oval white or pink petals.

The fruit is a capsule containing shiny, sometimes iridescent, black seeds.