Syndactyly is the most common congenital malformation of the limbs, characterized by the webbing or fusing together of two or more fingers or toes. Syndactyly exhibits a large degree of variation; digits can be partially fused or can be fused along their entire length. The fusion can be simple, with the digits connected only by skin, or it can be complex, with shared bones, nerves, blood vessels, or nails.

Syndactyly results from an error in fetal development, usually caused by a genetic defect. It can occur by itself as an isolated condition, or as one of several symptoms of a multi-symptom disease. Conditions associated with syndactyly include, but are not limited to, Apert Syndrome, Poland Syndrome, Jarcho-Levin Syndrome, Pfeiffer Syndrome, Holt-Oramand Syndrome, and Edwards Syndrome. Syndactyly can be corrected surgically, usually with the addition of a skin graft.