大头针、波比大头针是人们（尤其是女性）常用来固定发形的首饰品。主要由金属或塑料的小别针或小夹子组成。最初理发师为女性顾客理发时，用它来别束头发使用。典型的发夹常被称作波比大头针，没有特别的额外装饰作用。这种发夹的外表涂上与用户发色相近（如黑、棕、金）、非引人注目的颜色。但也有些发夹有着精心装饰的仿珍宝镶嵌品。波比大头针的发明出自于19世纪后期欧美男性绅士时尚中发型复杂化趋势需求。1920年代初，一种使用波比大头针固定出来的短发型“波比发型”深受女士们的喜爱，由此，波比的大头针在理发业与装饰业中扎下了根基。波比大头针廉价且易大批制造，很快便风靡欧美大陆。为了配合不同发色的用户，制造商开始给大头针涂上了色漆。1920年代末，据统计有90%的北美妇女使用。

A bobby pin (also known as a kirby grip or hair grip in the United Kingdom) is a type of hairpin, usually of metal or plastic, used in coiffure to hold hair in place. It is a small double-pronged hair pin or clip that slides into hair with the prongs open and then the flexible prongs close over the hair to hold it in place. They are typically plain and unobtrusively colored, but some are elaborately decorated or jeweled. Bobby pins became popular in the 1920s to hold the new bobbed hairstyles.