Darning is a sewing technique for repairing holes or worn areas in fabric or knitting using needle and thread alone. It is often done by hand, but using a sewing machine is also possible. Hand darning employs the darning stitch, a simple running stitch in which the thread is "woven" in rows along the grain of the fabric, with the stitcher reversing direction at the end of each row, and then filling in the framework thus created, as if weaving. Darning is a traditional method for repairing fabric damage or holes that do not run along a seam, and where patching is impractical or would create discomfort for the wearer, such as on the heel of a sock.

Darning also refers to any of several needlework techniques that are worked using darning stitches:

In its simplest form, darning consists of anchoring the thread in the fabric on the edge of the hole and carrying it across the gap. It is then anchored on the other side, usually with a running stitch or two. If enough threads are criss-crossed over the hole, the hole will eventually be covered with a mass of thread.

Fine darning, sometimes known as Belgian darning, attempts to make the repair as invisible and neat as possible. Often the hole is cut into a square or darn blends into the fabric.

There are many varieties of fine darning. Simple over-and-under weaving of threads can be replaced by various fancy weaves, such as twills, chevrons, etc., achieved by skipping threads in regular patterns.

Invisible darning is the epitome of this attempt at restoring the fabric to its original integrity. Threads from the original weaving are unraveled from a hem or seam and used to effect the repair. Invisible darning is appropriate for extremely expensive fabrics and items of apparel.

In machine darning, lines of machine running stitch are run back and forth across the hole, then the fabric is rotated and more lines run at right angles.

There are special tools for darning socks or stockings: