A polybag is a plastic bag sealed around a periodical such as a magazine or a comic book. Originally used by publishers for the protection of subscription issues, polybags became more common in the 1990s as a way to add an extra incentive, such as a trading card, poster or CD, to the purchase. Polybagged magazines also often contain subscription offer cards, and more recently, advertisements.

During the "Speculator Boom" of the 1990s, comic book publishers began to bag many of their comics, usually with a "special cover" (i.e. glow-in-the-dark, embossed) or with a collectible incentive inside. Fans had to choose between either reading the comic book or keeping it in pristine condition for potential financial gain, or doing both by buying two copies.

In addition to holding subscription offer cards and advertisements, Playboy Magazine's polybag is black for subscribers' privacy.