Syringa genus_authority = Mill. (Philip Miller) subdivision_ranks = Species subdivision = About 20 species; see text.

Syringa (Lilac) is a genus of about 20-25 species of flowering (flowering plant) woody plants in the olive family (Oleaceae), native to woodland and scrub from southeastern Europe to eastern Asia.

They are deciduous shrubs or small trees, ranging in size from 2-10 m tall, with stems up to 20-30 cm diameter. The leaves (leaf) are opposite (occasionally in whorls of three) in arrangement (Phyllotaxis), and their shape (Leaf shape) is simple and heart-shaped to broad lanceolate in most species, but pinnate in a few species (e.g. S. protolaciniata, S. pinnatifolia). The flowers are produced in spring, each flower being 5-10 mm in diameter with a four-lobed corolla (Corolla (flower)), the corolla tube narrow, 5-20 mm long; they are bisexual (plant sexuality), with fertile stamens and stigma (Gynoecium) in each flower. The usual flower colour is a shade of purple (often a light purple or lilac (lilac (color))), but white, pale yellow and pink, and even a dark burgundy color are also found. The flowers grow in large panicles, and in several species have a strong fragrance. Flowering varies between mid spring to early summer, depending on the species. The fruit is a dry, brown capsule (capsule (fruit)), splitting in two at maturity to release the two winged seeds.

The genus is most closely related to Ligustrum (privet), classified with it in Oleaceae tribus Oleeae subtribus Ligustrinae.

Lilacs are used as food plants by the larvae of some Lepidoptera species including Copper Underwing, Scalloped Oak and Svenssons Copper Underwing and Saras.