Linen is a textile made from the fibers of the flax plant. Linen is laborious to manufacture, but the fiber is very absorbent and garments made of linen are valued for their exceptional coolness and freshness in hot weather.

Linen fabric feels cool to the touch. It is smooth, making the finished fabric lint-free, and gets softer the more it is washed. However, constant creasing in the same place in sharp folds will tend to break the linen threads. This wear can show up in collars, hems, and any area that is iron creased during laundering. So it is better to hang your linen clothes rather than fold it.  Linen has less elasticity compare to cotton and does not spring back readily, explaining why it wrinkles so easily.

Linen fabric typically varies somewhat in thickness and is crisp and textured, but it can in some cases feel stiff and rough, and in other cases feel soft and smooth. When properly prepared, linen fabric has the ability to absorb and lose water rapidly. Linen can absorb a fair amount of moisture without feeling unpleasantly damp to the skin.

A characteristic often associated with linen yarn is the presence of “slubs”, or small knots which occur randomly along its length. However, in the case of many present-day linen fabrics,  slubs are considered as part of the aesthetic appeal of an expensive natural product. In addition, slubs do not compromise the integrity of the fabric, and therefore they are not viewed as a defect.

Many products are made of linen: aprons, bags, towels (swimming, bath, beach, body and wash towels), napkins, bed linens, tablecloths, runners, chair covers, and men's and women's wear.

The word linen is of West Germanic origin and cognate to the Latin name for the flax plant, linum, and the earlier Greek λινόν (linón). This word history has given rise to a number of other terms in English, most notably line, from the use of a linen (flax) thread to determine a straight line.

The collective term "linens" is still often used generically to describe a class of woven or knitted bed, bath, table and kitchen textiles traditionally made of linen. In the past, "linens" also referred to lightweight undergarments such as shirts, chemises, waist-shirts, lingerie (a word also cognate with linen), and detachable shirt collars and cuffs, all of which were historically made almost exclusively out of linen. The inner layer of fine composite cloth garments (as for example jackets) was traditionally made of linen, hence the word lining.

Linen textiles appear to be some of the oldest in the world: their history goes back many thousands of years. Fragments of straw, seeds, fibers, yarns, and various types of fabrics dating to about 8000 BC have been found in Swiss lake dwellings. Dyed flax fibers found in a prehistoric cave in Georgia suggest the use of woven linen fabrics from wild flax may date back even earlier to 36,000 BP.

Linen was sometimes used as currency in ancient Egypt. Egyptian mummies were wrapped in linen as a symbol of light and purity, and as a display of wealth. Some of these fabrics, woven from hand-spun yarns, were very fine for their day, but are coarse compared to modern linen. In 1923 the German city Bielefeld issued banknotes printed on linen. Today, linen is usually an expensive textile produced in relatively small quantities. It has a long "staple" (individual fiber length) relative to cotton and other natural fibers.