The dust jacket (sometimes book jacket, dust wrapper or dust cover) of a book is the detachable outer cover, usually made of paper and printed with text and illustrations. This outer cover has folded flaps that hold it to the front and back book covers.

Dust jackets originally displayed cover information on top of a simple binding, at a time when it was not feasible to print directly onto the binding. The role of a dust jacket has been largely supplanted by modern hardcover printing technologies, which prints such information directly onto the binding.

Modern dust covers still serve to display promotional material and shield the book from damage. The back panel or flaps of the dust cover are printed with biographical information about the author, a summary of the book from the publisher (known as a blurb) or critical praise from celebrities or authorities in the book's subject area. The information on the dust jacket often resembles that of the binding but may have additional promotions about an edition, and the information on the flaps is not typically copied onto the binding.

The dust jacket protects the book covers from damage. However, since it is itself relatively fragile, and since dust jackets have practical, aesthetic, and sometimes financial value, the jacket may in turn be wrapped in another jacket, usually transparent, especially if the book is a library volume.