Worsted ( or ) is a high-quality type of wool yarn, the fabric made from this yarn, and a yarn weight category. The name derives from Worstead, a village in the English county of Norfolk. That village, together with North Walsham and Aylsham, formed a manufacturing centre for yarn and cloth in the 12th century, when pasture enclosure and liming rendered the East Anglian soil too rich for the older agrarian sheep breeds. In the same period, many weavers from the County of Flanders moved to Norfolk. "Worsted" yarns/fabrics are distinct from woollens (though both are made from sheep's wool): the former is considered stronger, finer, smoother, and harder than the latter.

Worsted was made from the long-staple pasture wool from sheep breeds such as Teeswaters, Old Leicester Longwool and Romney Marsh. Pasture wool was not carded; instead it was washed, gilled and combed (using heated long-tooth metal combs), oiled and finally spun. When woven, worsteds were scoured but not fulled.

Both worsted and woolen spun wool are used for knitted fabrics. Worsted wool fabric is typically used in the making of tailored garments such as suits. In tropical-weight worsteds, the use of tightly spun, straightened wool combined with a looser weave permits air to flow through the fabric. Worsted is also used for carpets, clothing, hosiery, gloves and baize.