Spartina densiflora is a species of grass known by the common name denseflower cordgrass. It is native to the coastline of southern South America, where it is a resident of salt marshes. It is also known on the west coast of the North America and parts of the Mediterranean coast as an introduced species and in some areas a noxious weed. In California it is a troublesome invasive species of marshes in San Francisco Bay and in Humboldt Bay, where it was introduced during the 19th century from Chile in ballast.