Backstitch or back stitch and its variants stem stitch, outline stitch and split stitch are a class of embroidery and sewing stitches in which individual stitches are made backward to the general direction of sewing. These stitches form lines and are most often used to outline shapes or to add fine detail to an embroidered picture.

Basic backstitch is used to outline shapes in modern cross-stitch, in Assisi embroidery and occasionally in blackwork.

A versatile and easy to work stitch, backstitch is ideal for following both smooth and complicated outlines and as a foundation row for more complex embroidery stitches such as Herringbone ladder filling stitch. Although superficially similar to Holbein stitch, commonly used in Blackwork embroidery, backstitch differs in the way it is worked, requiring a single journey only to complete a line of stitching.

Stem stitch is an ancient technique; surviving mantles embroidered with stem stitch by the Paracas people of Peru are dated to the first century BCE. Stem stitch is used in the Bayeux Tapestry, an embroidered cloth probably dating to the later 1070s, for lettering and to outline areas filled with couching or laid-work.