Blue or blue-veined cheeses are so-called because of the bluish or greenish veins that furrow the interior.

Production is similar to that of soft or non-cooked semi-soft cheeses, with one important exception: a culture (Penicillium glaucum roqueforti or Penicillium candidum) is incorporated with the curdled milk or otherwise sprayed onto the curds before being shaped to promote the development of mould in the interior. Ripening, which lasts several months, takes place in a humid place. In order to facilitate air circulation in the interior and to promote the development of veins, the cheese wheels are pierced with long stainless steel needles. This accelerates the normal development of the cheese and means that quite strong tasting cheese is produced within a few months.

These cheeses generally have assertive flavours. Some of the most renowned cheeses are of this type, including Roquefort, Gorgonzola and Stilton, each with its own distinctive colour, flavour, texture and aroma. However, there are also blue variants of many other cheeses, such as Blue Cheshire .