Stellaria irrigua is a species of flowering plant in the family Caryophyllaceae known by the common names umbrella starwort and umbellate starwort. It is native to western North America from Alaska and north-western Canada to the south-western United States, as well as parts of Asia, including Siberia. It grows in subalpine and alpine climates in mountain forests and riverbanks. It is a rhizomatous perennial herb producing a slender prostrate stem up to about 20 centimeters long, sometimes forming clumps or mats. The stem is lined with pairs of oval leaves each up to about 2 centimeters long. The inflorescence is an umbel-shaped array of several flowers each on an arching or erect pedicels. The flower has five pointed green sepals each no more than 3 millimeters long. There are occasionally tiny white petals within the calyx of sepals, but these are generally absent.