(Citrus paradisi), citrus tree of the Rutaceae family and its edible fruit. The grapefruit tree grows to be as large and vigorous as an orange tree; a mature tree may be from 4.5 to 6 metres (15 to 20 feet) high. The foliage is very dense, with leaves dark and shiny green and nearly glabrous. Flowers are large, white, borne singly or in clusters in the axils of the leaves; petals are similar to those of sweet orange but usually larger. Lemon-yellow when ripe, the fruit ranges from 100 to 150 mm (4 to 6 inches) in diameter and averages twice as large as a medium-sized orange, with size depending upon the variety and upon growing conditions. Its pulp is usually light yellowish, tender, and very full of juice, with a distinctive, mildly acid flavour. Several varieties have pink or red pulp. As a source of vitamin C, the grapefruit is exceeded among common fruits only by the orange and lemon.

The grapefruit probably originated in Jamaica as a hybrid of C. grandis. It became well established as a fruit for home consumption in the islands of the West Indies before its culture spread to the American mainland.

Grapefruit trees produce the best quality fruit on sandy, relatively fertile soils. Supplementary fertilization is necessary in practically all producing areas in the United States. The trees come into bearing early and may be expected to produce commercially profitable crops by the fourth to sixth year after being planted in the orchard. Mature trees may produce remarkably large crops—585 to 675 kg (1,290 to 1,490 pounds) of fruit per tree. In the 1980s, 60 percent of world production was in the United States, mainly in Florida, Texas, Arizona, and California. Grapefruit has become popular as breakfast fruit in various parts of the world, and production has expanded to other citrus-growing countries, notably Israel, Cyprus, South Africa, and Brazil. More than half of the United States' crop is canned or frozen.