A shamrock is a type of clover, used as a symbol of Ireland. Saint Patrick, one of Ireland's patron saints, is said to have used it as a metaphor for the Christian Holy Trinity. The name shamrock comes from Irish seamróg, which is the diminutive of the Irish word seamair and simply means "young clover".

Clover, also called trefoil, are plants of the genus Trifolium, consisting of about 300 species of flowering plants in the legume family Fabaceae originating in Europe. The genus has a cosmopolitan distribution with highest diversity in the temperate Northern Hemisphere, but many species also occur in South America and Africa, including at high altitudes on mountains in the tropics. They are small annual, biennial, or short-lived perennial herbaceous plants, typically growing up to 30 centimetres (12 in) tall. The leaves are trifoliate, with stipules adnate to the leaf-stalk, and heads or dense spikes of small red, purple, white, or yellow flowers; the small, few-seeded pods are enclosed in the calyx. Other closely related genera often called clovers include Melilotus and Medicago.