Cabbage, comprising several cultivars of Brassica oleracea, is a leafy green, red (purple), or white (pale green) biennial plant grown as an annual vegetable crop for its dense-leaved heads. It is descended from the wild cabbage (B. oleracea var. oleracea), and belongs to the "cole crops" or brassicas, meaning it is closely related to broccoli and cauliflower (var. botrytis); Brussels sprouts (var. gemmifera); and Savoy cabbage (var. sabauda).

A cabbage generally weighs between 500 and 1,000 grams (1 and 2 lb). Smooth-leafed, firm-headed green cabbages are the most common, with smooth-leafed purple cabbages and crinkle-leafed savoy cabbages of both colours being rarer. Under conditions of long sunny days, such as those found at high northern latitudes in summer, cabbages can grow quite large. As of 2012, the heaviest cabbage was 62.71 kilograms (138 lb 4 oz). Cabbage heads are generally picked during the first year of the plant's life cycle, but plants intended for seed are allowed to grow a second year and must be kept separate from other cole crops to prevent cross-pollination. Cabbage is prone to several nutrient deficiencies, as well as to multiple pests, and bacterial and fungal diseases.

Cabbage was most likely domesticated somewhere in Europe in ancient history before 1000 BC. Cabbage use in cuisine has been documented since Antiquity. It was described as a table luxury in the Roman Empire. By the Middle Ages, cabbage had become a prominent part of European cuisine, as indicated by manuscript illuminations. New variates were introduced from the Renaissance on, mostly by Germanic-speaking peoples. Savoy cabbage was developed in the 16th century. By the 17th and 18th centuries, cabbage was popularised as staple food in central, northern, and eastern Europe. It was also employed by European sailors to prevent scurvy during long ship voyages at sea. Starting in the Early Modern Era, cabbage was exported to the Americas, Asia, and around the world.

They can be prepared many different ways for eating; they can be pickled, fermented (for dishes such as sauerkraut), steamed, stewed, roasted, sautéed, braised, or eaten raw. Raw cabbage is a rich source of vitamin K, vitamin C, and dietary fiber. World production of cabbage and other brassicas in 2020 was 71 million tonnes, led by China with 48% of the total.