A pillbox hat is a small women's hat in a simple, understated style. Pillbox hats were immensely popular from the 1930s through the 1960s, and they continue to be worn today by some women, in addition to styles which have diverged slightly from the traditional pillbox. Many hat stores carry pillbox hats in a variety of colors and styles, and they can also be ordered from companies which specialize in the production of hats.

A classic pillbox hat has a flat crown, and smooth, straight sides. The hat is typically made from a material which is sturdy enough to hold the shape of the hat; felt is a popular choice. The shape of a pillbox hat is sort of reminiscent of a box designed to hold pills, although these hats are obviously larger than pill boxes.

Classically, the pillbox hat is small enough that it must be pinned on the head, because the brim is too narrow to go over the head. During the period when the pillbox hat was fashionable, the bouffant hairdo was very popular among women, and many women topped this bold, large hairstyle with a jauntily pinned pillbox hat, strategically placed so that it would not crush the hairstyle. People can choose to use decorative visible hatpins with a pillbox hat, or discreet hidden pins to secure the hat.

One the most notable wearers of the pillbox hat was American First Lady Jacqueline Kennedy, who popularized the pillbox from day one in the White House, when she wore a bone-white pillbox hat to her husband's inauguration. Many Americans also have vivid memories of the coordinating pink suit and pillbox hat she wore on the date of her husband's assassination; the pillbox hat experienced a marked decline briefly as a result of being so closely associated with this unfortunate event.

The understated design of the pillbox hat can be dressed up with a veil or pin, or left plain. Some women use the pillbox hat as a church hat, since the simple, flattering style is appropriately somber and respectful for church. Others wear a more updated version of the pillbox hat, with a cuff in a contrasting color and a soft fabric construction which gives the hat a more casual, rumpled look.