Interfacing fabric is a type of material used in sewing to provide structure, support, and stability to various parts of garments and projects. It is typically a lightweight fabric that is applied to specific areas of a garment, such as collars, cuffs, waistbands, and buttonholes, to add strength, shape, and reinforcement.

Fusible/ Iron on interfacing has adhesive on one side that can be activated with heat, often through ironing, to bond the interfacing to the main fabric. Sew-in interfacing requires stitching to attach it to the fabric.