Allium giganteum, common name giant onion, is an Asian species of onion, native to central and southwestern Asia, but cultivated in many countries as a flowering garden plant. It is the largest Allium species in common cultivation, reaching 1.5 meters (4.9 ft).
In early to mid-summer, small globes of intense purple umbels appear, followed by attractive fruiting umbels. A popular cultivar, ‘Globemaster’, is shorter (80 centimeters (31 in)) but produces much larger, dark purple umbels (15–20 centimeters (5.9–7.9 in)). Both varieties have received the Royal Horticultural Society’s Award of Garden Merit.