Of all introduced broadleaves, Sweet Chestnut is perhaps best suited to Britain and Ireland, long valued for its strong, durable, easily cleft timber and delicious nuts. Also called Spanish Chestnut. It is thought to have been cultivated and spread by the Romans, including to Britain (where it is an archaeophyte), and is classed a neophyte in Ireland.

Its native range skirts the northern fringes of the Mediterranean Sea (Portugal, Spain, France, Italy, Greece), and southern fringes of the Black Sea.

Monoecious, with fairly erect bisexual catkins (female at the base, male towards the tips) plus separate female-flower clusters at shoot tips. The sticky, sweet-smelling pollen is wind- and insect-dispersed, and up to three nuts (achenes) form in prickly cupules dispersed by birds and mammals. In cooler, more northerly conditions it may not set viable seed. It can also propagate by layering into clonal stands.

A tall tree (35m), strongly branched, with a broad crown and massive trunk in the open but a long slender trunk and narrow upper crown in forest. Bark silver-grey with horizontal bands, becoming cracked, corky and often spirally ridged in old trees. Twigs grey-brown, with knobbly buttressed buds and an aborted terminal bud. Leaves oblong, slender, leathery, sharply serrate with forward-curving bristly tips. Flowers erect, catkin-like, from leaf axils. Cupule spiny, with 2-4 chestnuts.

Grows in most well-drained soils but dislikes shade. It can be coppiced, usually on 12-16-year cycles, and timber trees are felled before growing too large, as the wood can develop internal 'shake' (splits). Grafted cultivars for nuts include 'Marigoule', 'Marron De Lyon' and 'Regal', and ornamental variegated and cut-leaved forms are available.

Flowers are a valued source of nectar for insects, while nuts are favoured by birds and mammals.

Chestnut blight, caused by the fungus Cryphonectria parasitica, decimated the American Chestnut and is now a serious European concern, so far found on only a few sites in south-east England. Imported seed, young plants, timber and bark are all possible vectors for its long-distance spread.

A valuable timber tree, with hardwood like oak but more durable, suiting house and barn framing, piles and fencing, though it can suffer shake (linked to age and spiral bark). Coppice products include rails, cleft pales and tent pegs. The nuts are delicious roasted and also make a sweet flour.