The grapefruit is a subtropical citrus tree grown for its bitter fruit, an 18th-century hybrid first bred in Jamaica. When found in Barbados it was named the "forbidden fruit"; it is also called the "shaddock", after its creator.

These evergreen trees are usually found at around 5–6 metres (16–20 ft) tall, although they can reach 13–15 metres (43–49 ft). The leaves are dark green, long (up to 150 mm, or 6 inches) and thin. It produces 5 cm (2 in) white four-petaled flowers. The fruit is yellow-orange skinned and largely oblate, and ranges in diameter from 10–15 cm. The flesh is segmented and acidic, varying in color depending on the cultivars, which include white, pink and red pulps of varying sweetness. The 1929 US Ruby Red (of the Redblush variety) has the first grapefruit patent.

The fruit has only become popular from the late 19th century; before that it was only grown as an ornamental plant. The US quickly became a major producer of the fruit, with orchards in Florida, Texas, Arizona, and California. In Spanish, the fruit is known as toronja or pomelo.

One ancestor was the Jamaican sweet orange (Citrus sinensis); the other was the Indonesian pomelo (Citrus maxima). Captain Shaddock brought pumelo seeds to Jamaica and bred the first fruit. It is closer to the orange.

The hybrid fruit was in 1750 documented by the Rev. Griffith Hughes describing specimens from Barbados. Currently, the grapefruit is said to be one of the...