Gardenia jasminoides, commonly known as gardenia and cape jasmine, is an evergreen flowering plant in the coffee family Rubiaceae. It is native to the subtropical and northern tropical parts of the Far East. Wild plants range from 30 centimetres to 3 metres (about 1 to 10 feet) in height. They have a rounded habit with very dense branches with opposite leaves that are lanceolate-oblong, leathery or gathered in groups on the same node and by a dark green, shiny and slightly waxy surface and prominent veins.

With its shiny green leaves and heavily fragrant white summer flowers, it is widely used in gardens in tropical, subtropical, and warm temperate climates. It also is used as a houseplant in temperate climates. It has been in cultivation in China for at least a thousand years, and it was introduced to English gardens in the mid-18th century. Many varieties have been bred for horticulture, with low-growing, and large, and long-flowering forms.

Gardenia jasminoides is a shrub that ranges from 30 cm to 3 m (1–10 ft) high in the wild, with cylindrical to flat branches that at first are covered with caducous hairs that fall early, leaving the branch smooth. The leaves are in opposite pairs or rarely in groups of three along the branches. They are either subsessile (almost without a petiole) or on short 0.5–1 centimetre (0.2–0.4 inches) petioles. The leaves themselves are 3–25 cm (1.2–9.8 in) long by 1.5–8 cm (0.6–3.1 in) wide and can be oblong-lanceolate, obovate-oblong, obovate, oblanceolate, or elliptic in shape. Their upper surface is smooth and shiny, or slightly hairy along the primary veins, while the undersurface is sparsely hairy to smooth. Each leaf has 8 to 15 pairs of secondary veins. The flowers are solitary and terminal, arising from the ends of the stems.

The white flowers have a matte texture, in contrast to the glossy leaves. They gradually take on a creamy yellow color and a waxy surface. They can be quite large, up to 10 cm (4 in) in diameter, loosely funnel-shaped, and there are double-flowered forms. Blooming in summer and autumn, they are among the most strongly fragrant of all flowers. They are followed by small and oval fruits.

The flowers of jasmine gardenia are all simultaneous hermaphrodites.

German-Dutch botanist Georg Rumphius had seen Gardenia jasminoides on the island of Amboina (Ambon), noting in his Herbarium Amboinense around 1700 that it was a "delightful ornament" called catsjopiri or catsjopiring in Malay. He reported that it had been imported there from Batavia (Jakarta). Swedish taxonomist Carl Linnaeus recognized the value of Rumphius' work and assigned his student Olaf Stickman to study it. Stickman's dissertation was printed in 1754. He subsequently described the species as Varneria augusta in 1759.

English naturalist John Ellis described Gardenia jasminoides in 1761, having realised on dissecting the flower that it was not closely related to jasmine and warranted a new genus. He had initially proposed Warneria after the original plant's owner in England. However, Warner declined to have it named for him and so Ellis chose Gardenia to honour Scottish naturalist Alexander Garden. Ellis had also proposed Augusta as a generic name, which Linnaeus rejected. It gained its association with the name jasmine when botanist and artist Georg Dionysius Ehret depicted it. Ehret queried whether it was a jasmine because the flowers resembled the plant. The name stuck and lived on as common name and scientific epithet.

Linnaeus gave it the name Gardenia florida in 1762 in the second edition of his Species Plantarum. American botanist Elmer D. Merrill followed Stickman with Gardenia augusta in 1917; however, Rumphius' original work was later deemed insufficient to describe the species, so these names are nomina nuda.