Momordica charantia, known as bitter melonbitter gourdbitter squash, or balsam-pear, is a tropical and subtropical vine of the family Cucurbitaceae, widely grown in Asia, Africa, and the Caribbean for its edible fruit. Its many varieties differ substantially in the shape and bitterness of the fruit. Bitter melon also has names in other languages which have entered English as loanwords, e.g. goya from Okinawan, pākal (பாகல்) in Tamil and karela from Sanskrit. Those from the Caribbean island of Jamaica commonly refer to the plant as cerasee. In Brazil this plant is called Saint Cajetan’s Melon (melão-de-são-caetano).

Bitter melon originated in India and was introduced into China in the 14th century. It is widely used in East Asian, South Asian, and Southeast Asian cuisine.
This herbaceous, tendril-bearing vine grows up to 5 m (16 ft) in length. It bears simple, alternate leaves 4–12 cm (1.6–4.7 in) across, with three to seven deeply separated lobes. Each plant bears separate yellow male and female flowers. In the Northern Hemisphere, flowering occurs during June to July and fruiting during September to November.

The fruit has a distinct warty exterior and an oblong shape. It is hollow in cross-section, with a relatively thin layer of flesh surrounding a central seed cavity filled with large, flat seeds and pith. The fruit is most often eaten green, or as it is beginning to turn yellow. At this stage, the fruit’s flesh is crunchy and watery in texture, similar to cucumber, chayote or green bell pepper, but bitter. The skin is tender and edible. Seeds and pith appear white in unripe fruits; they are not intensely bitter and can be removed before cooking.

As the fruit grows, the flesh (rind) becomes somewhat tougher and more bitter, and many consider it too distasteful to eat. On the other hand, the pith becomes sweet and intensely red; it can be eaten uncooked in this state, and is a popular ingredient in some Southeast Asian salads.

When the fruit is fully ripe, it turns orange and mushy, and splits into segments which curl back dramatically to expose seeds covered in bright red pulp.

Bitter melon comes in a variety of shapes and sizes. The cultivar common in China is 20–30 cm (7.9–11.8 in) long, oblong with bluntly tapering ends and pale green in color, with a gently undulating, warty surface. The bitter melon more typical of India has a narrower shape with pointed ends, and a surface covered with jagged, triangular “teeth” and ridges. It is green to white in color. Between these two extremes are any number of intermediate forms. Some bear miniature fruit of only 6–10 cm (2.4–3.9 in) in length, which may be served individually as stuffed vegetables. These miniature fruit are popular in Bangladesh, India (common name ‘Karela’), Pakistan, Nepal and other countries in South Asia. The sub-continent variety is most popular in Bangladesh and India.

Bitter melon is generally consumed cooked in the green or early yellowing stage. The young shoots and leaves of the bitter melon may also be eaten as greens.

In Chinese cuisine, bitter melon (Chinese: 苦瓜, pinyin: kǔguā or kugua) is valued for its bitter flavor, typically in stir-fries (often with pork and douchi), soups, dim sum, and herbal teas (See Gohyah tea). It has also been used in place of hops as the bittering ingredient in some beers in China and Okinawa.

Bitter melon is very popular throughout India. In North Indian cuisine, it is often served with yogurt on the side to offset the bitterness, used in curry such as sabzi or stuffed with spices and then cooked in oil.

In South Indian cuisine, it is used in the dishes thoran/thuvaran (mixed with grated coconut), mezhukkupuratti (stir fried with spices), theeyal (cooked with roasted coconut) and pachadi (which is considered a medicinal food for diabetics). Other popular recipes include preparations with curry, deep fried with peanuts or other ground nuts, and Pachi Pulusu, a soup with fried onions and other spices. In Tamil Nadu, where it is known as paagarkaai or pavakai (பாகற்காய்) in Tamil, a special preparation called pagarkai pitla, a kind of sour koottu, variety is very popular. Also popular is kattu pagarkkai, a curry that involves stuffing with onions, cooked lentil and grated coconut mix, tied with thread and fried in oil. In the Konkan region of Maharashtra, salt is added to finely chopped bitter gourd, known as karle (कारले) in Marathi, and then it is squeezed, removing its bitter juice to some extent. After frying this with different spices, the less bitter and crispy preparation is served with grated coconut. In Kannada it is known as haagalakaayi.

In northern India and Nepal, bitter melon, known as tite karela (तीते करेला) in Nepali, is prepared as a fresh pickle. For this, the vegetable is cut into cubes or slices, and sautéed with oil and a sprinkle of water. When it is softened and reduced, it is crushed in a mortar with a few cloves of garlic, salt and a red or green pepper. It is also eaten sautéed to golden-brown, stuffed, or as a curry on its own or with potatoes.

In Sri Lanka it is known as karavila (කරවිල) in Sinhala, and is an ingredient in many different curry dishes (e.g., Karawila Curry and Karawila Sambol) which are served mainly with rice in a main meal. Sometimes large grated coconut pieces are added, which is more common in rural areas. Karawila juice is also sometimes served there.

In Pakistan, known as karela (کریلا) in Urdu-speaking areas, and Bangladesh, known as korola (করলা|করলা) in Bengali, bitter melon is often cooked with onions, red chili powder, turmeric powder, salt, coriander powder, and a pinch of cumin seeds. Another dish in Pakistan calls for whole, unpeeled bitter melon to be boiled and then stuffed with cooked minced beef, served with either hot tandoori bread, naanchappati, or with khichri (a mixture of lentils and rice).