Grosgrain ( GROH-grayn, also sometimes GROS-grayn) is a type of fabric or ribbon defined by the fact that its weft is heavier than its warp, creating prominent transverse ribs. Grosgrain is a plain weave corded fabric, with heavier cords than poplin but lighter than faille, and is known for being a firm, close-woven, fine-corded fabric. Grosgrain has a dull appearance, with little luster in comparison to many fabric weaves, such as satin, often used for ribbons; however, it is comparatively very strong. Grosgrain fabric is most commonly available in black, but grosgrain ribbon comes in a large variety of colors and patterns. The ribbon is very similar to Petersham ribbon in its appearance, but it does not have the ability to follow the curves of a surface or edge the way that the latter does.

"Grosgrain" is commonly used to refer to a heavy, stiff ribbon of silk or nylon woven via taffeta weave using a heavy weft, which results in distinct transverse ribs. Historically, grosgrain was made from wool, silk, or a combination of fibers such as silk and wool or silk and mohair. When a combination of fibers was used, the end result was sometimes given the name grogram, silk mohair, gros de Tours or gros de Napels.