Kongl. Vetensk. Acad. Nya Handl. 21: 239. 1800.
Herbs, epiphytic or terrestrial, ± cespitose. Stems pseudobulbs, green, ovoid. Leaves persistent, 1–3, not recurved; blade conduplicate, linear-lanceolate, dorsiventrally flattened, margins entire. Inflorescences paniculate racemes, lateral branches to 10[–42] cm; bracts narrowly triangular. Flowers resupinate; sepals and petals distinct and free, oblong-elliptic, obovate to nearly quadrangular or nearly circular, apex retuse to obtuse, sometimes apiculate; lip pandurate, 3-lobed; callus prominent warty-tuberculate-fringed; column with wings, arms, or fingerlike projections; stigmatic cavity ± round; rostellum not prominent. Fruits capsules.
Tropical and subtropical, Western Hemisphere.
Species 800 (1 in the flora).
Oncidium is a large polymorphic, and probably paraphyletic, assemblage.