A guide book is a book for tourists or travelers that provides details about a geographic location, tourist destination, or itinerary. It is the written equivalent of a tour guide. Many travel guides now take the form of travel websites rather than printed books.

It will usually include details such as phone numbers, addresses, prices and reviews of hotels and other lodgings, restaurants, and activities. Maps of varying detail are often included. Sometimes historical and cultural information is also provided. Different guide books may focus on different aspects of travel, from adventure travel to relaxation, or be aimed at travelers with larger or smaller travel budgets, or focus on the particular interests and concerns of certain groups such as sexual orientation or dietary restrictions. Guide books are generally intended to be used in conjunction with actual travel, although simply enjoying a guide book with little or no intention of visiting may be referred to as "armchair tourism".

The periplus was an itinerary from landmark to landmark of the ports along a coast, a forerunner of the guide. A periplus such as the Periplus of the Erythraean Sea was a manuscript document that listed, in order, the ports and coastal landmarks, with approximate intervening distances, that the captain of a vessel could expect to find along a shore. It served the same purpose as the later Roman itinerarium of road stops.