Sempervivum arachnoideum, the cobweb house-leek,[1] is a species of flowering plant in the family Crassulaceae, native to European mountains, in the Alps, Apennines and Carpathians.

Growing to 8 cm (3 in) tall by 30 cm (12 in) wide, it is a rosette-forming succulent perennial, valued in cultivation for its ability to colonise hot, dry areas via offsets.

[2] The specific epithet arachnoideum refers to its furry central rosettes (long ciliate leaf margins), resembling spider webs.

This plant,[4] and the subspecies Sempervivum arachnoideum subsp.

tomentosum,[5] have gained the Royal Horticultural Society's Award of Garden Merit.