Cerastium diffusum, the fourstamen chickweed[1] or sea mouse-ear,[2] is a species of flowering plant in the pink and carnation family Caryophyllaceae.

It is an annual herb, to 30 cm.high, occurring in western Europe and northern Africa.

Found mainly in coastal areas of Algeria, the Baleares, Belgium, Corsica, Denmark, France, the Faroe Islands, Germany, Great Britain, Ireland, Italy, Libya, Morocco, Netherlands, Norway, Portugal, Sardinia, Sicily, Spain and Sweden.

[3] The flowers have 4, (or seldom 5) petals, 4 or 5 stamens appearing between March and May.

The leaves are opposite, (sessile) without petioles and the sepals and bracts are all green, without pale margins.