A preface is an introduction to a book or other literary work written by the works author. It is often confused with a foreword, which is an introductory essay written by a different person and precedes an authors preface. The preface often covers the story of how the book came into being, or how the idea for the book was developed, and may be followed by thanks and acknowledgments to people who were helpful to the author during the time of writing. A preface is often signed, and the date and place of writing often follow the typeset signature.

The term preface can also mean any preliminary or introductory statement. It is sometimes abbreviated pref. The word preface comes from Latin, meaning either "spoken before" or "made before". While the former source of the word could have preface meaning the same as prologue, the latter strongly implies an introduction written before the body of the book.

In summary, a preface is an introductory passage written about a book by its author, which lays out why the book exists, its subject matter, and its goals. It is different from a foreword, which is written by a different person and provides an introductory essay.