Grevillea is a diverse genus of about 360 species of evergreen flowering plants in the protea family Proteaceae, native to rainforest and more open habitats in Australia, New Guinea, New Caledonia, Indonesia and Sulawesi. It was named in honour of Charles Francis Greville. The species range from prostrate shrubs less than 50 cm (20 in) tall to trees 35 m (115 ft) tall. Common names include grevillea, spider flower, silky oak and toothbrush plant. Closely related to the genus Hakea, the genus gives its name to the subfamily Grevilleoideae.

The brightly coloured, petal-less flowers consist of a calyx tube that splits into 4 lobes with long styles.

Central America (where the greatest diversity occurs), Mexico, the Antilles, southeastern United States, Australia, Melanesia, Micronesia, Japan, China, Southeast Asia, India, Sri Lanka, Madagascar, and southern and tropical Africa, where at least 65 species occur.

Many species of grevilleas are popular garden plants, especially in Australia but also in other temperate and subtropical climates.

Many grevilleas have a propensity to interbreed freely, and extensive hybridisation and selection of horticulturally desirable attributes has led to the commercial release of many named Grevillea cultivars.

Among the best known are Grevillea 'Robyn Gordon', a small shrub up to 1.5 m (5 ft) high and wide which can flower 12 months of the year in subtropical climates. The cultivar 'Canberra Gem' has gained the Royal Horticultural Society's Award of Garden Merit.

They can be grown from soft tip cuttings from December-March (in the Southern Hemisphere) or seed. Many harder-to-grow species can be grafted onto hardy rootstock such as Grevillea robusta.

There is an active Grevillea Study Group in the Australian Native Plants Society for people interested in Grevilleas, both for uses in horticulture and for conservation in the wild.

Grevillea flowers were a traditional favourite among Aborigines for their sweet nectar. This could be shaken onto the hand to enjoy, or into a coolamon with a little water to make a sweet drink. They might be referred to as the original "bush lollies". Drinking nectar direct from the flower is best avoided as some commonly cultivated Grevillea species produce flowers containing toxic cyanide.