Stellaria longifolia is a species of flowering plant in the family Caryophyllaceae known by the common name longleaf starwort.

It grows in many types of moist habitat, including meadows, marshes, and roadsides.

It is a rhizomatous perennial herb forming clumps with sprawling, branching stems which are mostly hairless except for tiny rough hairs along the edges of the squarish stem.

The linear to lance-shaped leaves are up to 3.5 centimeters long and are oppositely arranged in pairs.

The flower has five pointed green sepals each a few millimeters long.