A hairpin or hair pin is a long device used to hold a person's hair in place. It may be used simply to secure long hair out of the way for convenience or as part of an elaborate hairstyle or coiffure. The earliest evidence for dressing the hair may be seen in carved "Venus figurines" such as the Venus of Brassempouy and the Venus of Willendorf. The creation of different hairstyles, especially among women, seems to be common to all cultures and all periods and many past, and current, societies use hairpins.

Hairpins made of metal, ivory, bronze, carved wood, etc. were used in ancient Egypt. for securing decorated hairstyles. Such hairpins suggest, as graves show, that many were luxury objects among the Egyptians and later the Greeks, Etruscans, and Romans. Major success came in 1901 with the invention of the spiral hairpin by New Zealand inventor Ernest Godward. This was a predecessor of the hair clip.

The hairpin may be decorative and encrusted with jewels and ornaments, or it may be utilitarian, and designed to be almost invisible while holding a hairstyle in place. Some hairpins are a single straight pin, but modern versions are more likely to be constructed from different lengths of wire that are bent in half with a u-shaped end and a few kinks along the two opposite portions. The finished pin may vary from two to six inches in last length. The length of the wires enables placement in several designs of hairstyles to hold the nature in place. The kinks enable retaining the pin during normal movements.

A hairpin patent was issued to Kelly Chamandy in 1925.