Agastache foeniculum (blue giant hyssop; syn. Agastache anethiodora (Nutt.) Britton), commonly called anise hyssop, blue giant hyssop, Fragrant giant hyssop, or the lavender giant hyssop, is a species of perennial plant in the mint family, (Lamiaceae). This plant is native to much of north-central and northern North America, notably the Great Plains and other prairies, and can be found in areas of Canada. It is tolerant of deer and drought, and also attracts hummingbirds, butterflies, bumblebees, honeybees, carpenter bees, and night flying moths.

Anise hyssop is in the same family as hyssop (the mint family Lamiaceae), but they are not closely related. Hyssop (Hyssopus) is a genus of about 10-12 species of herbaceous or semi-woody plants native from the east Mediterranean to central Asia.

This species grows from 2 ft (61 cm) to 4 ft (120 cm) tall and 1 ft (30 cm) wide, in a clump-like, upright shape, with flowers appearing in showy verticillasters, or false whorls, and occasionally branching at the apex. The leaves have an oval, toothed shape with a white tint underneath. The plant blooms in June to Septe