Lilium is a type of herbaceous flowering plants growing from bulbs. Most species are local to the temperate northern hemisphere. They comprise a genus of about 110 species in the lily family (Liliaceae).

They are important as large showy flowering garden plants. Additionally, they are important culturally and in literature on much of the earth. Some species are sometimes grown or harvested for the edible bulbs.The species in this genus are the true lilies. Many other plants exist with "lily" in the common English name, some of which are unrelated to the true lilies

Lilies are leafy stemmed herbs. They form nude or tunic-less scaly underground bulbs which are their overwintering organs. In some North American species the bottom of the bulb develops into rhizomes, on which numerous small bulbs are found. Some species grow stolons. Most bulbs are deeply buried, but a few species form bulbs near the soil surface. Many species form stem-roots. With those, the bulb grows naturally at some depth in the soil, and each year the new stem puts out adventitious roots above the bulb as it emerges from the soil. These roots are in addition to the basal roots that build at the base of the bulb..