Kirschner wires or K-wires or pins are sterilized, sharpened, smooth stainless steel pins. Introduced in 1909 by Martin Kirschner, the wires are now widely used in orthopedics and other types of medical and veterinary surgery. They come in different sizes and are used to hold bone fragments together (pin fixation) or to provide an anchor for skeletal traction. The pins are often driven into the bone through the skin (percutaneous pin fixation) using a power or hand drill. They also form part of the Ilizarov apparatus.

For hand fracture fixation, whether K-wires should be buried or left protruding from the skin remains a topic of debate and ongoing research.