Crambe maritima, common name sea kale, seakale or crambe, is a species of halophytic (salt-tolerant) flowering plant in the genus Crambe of the family Brassicaceae. It grows wild along the coasts of mainland Europe and the British Isles.

The plant is related to the cabbage and was first cultivated as a vegetable in Britain around the turn of the 18th century. The blanched stems are eaten as a vegetable, and became popular in the mid-19th century.

Growing to 75 cm (30 in) tall by 60 cm (24 in) wide, it is a mound-forming, spreading perennial. It has large fleshy glaucous collard-like leaves and abundant white flowers. The globular pods contain a single seed.

This species appears to be a European endemic, with a distribution generally confined to two discontinuous coastal regions of Europe; the species is absent from North Africa and the Middle East. It occurs in the Black Sea coasts of Bulgaria, Romania, Turkey, and Ukraine including the Crimea, but is absent from most of the Mediterranean, recurring again from northern France and the British Isles to the Baltic Sea. In the Iberian Peninsula, Greece and Italy it is replaced by the species Crambe hispanica, with which its distribution has been confused with until quite recently; the species is absent from Portugal, Greece, Italy and Spain, but is said to occur in Croatia.

Although it was once believed to be found growing in Israel and Jordan, or alternatively Lebanon and Syria, these populations are now classified as C. hispanica.

It is very rare in Northern Ireland, but has been recorded in Counties Down and Antrim, and in a number of other coastal counties in the island of Ireland. In England it is primarily found on the southeast coast (extensively along Chesil Beach in Dorset), but it also occurs on stretches of the East Anglian and Cumbrian coasts. In Wales it is found on the northern beaches and in Scotland in the extreme southwest.

It is uncommonly found along the coast of Norway, particularly so in the Færder National Park.

Crambe maritima is a halophyte, meaning that it tolerates salt and is therefore found on coastal beaches where little else thrives. It is usually found above high tide mark on beaches in which the sand includes pebbles or rock. A typical habitat for the species in Britain is vegetated shingle beaches, where it grows in association with yellow horned poppy and curled dock. It is the dominant plant species in plant communities found in fragmentary, endangered habitats on shingle beaches and bars on the southern Baltic coasts of Sweden, Finland and Estonia, east to Mecklenburg, where it grows together with Leymus arenarius, Euphorbia palustris, Honkenya peploides, Angelica archangelica subsp. litoralis, Atriplex spp., Beta vulgaris subsp. maritima, Elymus repens, Geranium robertianum subsp. rubricaule, Glaucium flavum, Isatis tinctoria, Ligusticum scoticum, Mertensia maritima, Silene uniflora, Tripleurospermum maritimum and Valeriana salina. Trapping wind-blown sand, clumps of sea kale may initiate the formation of dunes.