Euphorbia stygiana (Portuguese: Trovisco-macho) is a species of evergreen shrub in the family Euphorbiaceae, endemic to several islands of the Azores.

Euphorbia stygiana is an evergreen shrub with low but robust serpentine, green stems; white-veined, thick, leathery blue-dark green leaves and large yellow-green flower heads which are strongly honey-scented in spring and summer (from May to June).

[2][3][4] The leaves are 7–14 by 1.5–3.5 centimetres (2.76 in–5.51 in × 0.59 in–1.38 in) long, slightly pubescent on the bottom side.

[5] During cold winters (especially outside its native range) these leaves may turn to a brilliant crimson colour.

[4] Euphorbia stygiana is endemic to all Azorean islands except Graciosa where it inhabits the extremely humid highlands of the archipelago from 300 to 1,100 metres (980 to 3,610 ft) in altitude, especially on Pico Island, in sheltered places such as ravines, craters and dense laurel-Juniperus forests.