Gayophytum diffusum is a species of flowering plant in the evening primrose family known by the common name spreading groundsmoke.

It is native to western North America where it is a common member of many different habitats.

This is a spindly, branching annual herb reaching a maximum height of about half a meter.

Its thin stems have sparse narrow leaves a few centimeters long.

The fruit is a cylindrical, knobby capsule up to 1.5 centimeters long.