A travel document is an identity document issued by a government or international entity pursuant to international agreements to enable individuals to clear border control measures. Travel documents usually assure other governments that the bearer may return to the issuing country, and are often issued in booklet form to allow other governments to place visas as well as entry and exit stamps into them.

The most common travel document is a passport, which usually gives the bearer more privileges like visa-free access to certain countries. While passports issued by governments are the most common variety of travel document, many states and international organisations issue other varieties of travel documents that allow the holder to travel internationally to countries that recognise the documents. For example, stateless persons are not normally issued a national passport, but may be able to obtain a refugee travel document or the earlier "Nansen passport" which enables them to travel to countries which recognise the document, and sometimes to return to the issuing country.

Border control policies typically require travellers to present valid travel documents in order to ascertain their identity, nationality or permanent residence status, and eligibility to enter a given jurisdiction. The most common form of travel document is the passport, a booklet-form identity document issued by national authorities or the governments of certain subnational territories containing an individual's personal information as well as space for the authorities of other jurisdictions to affix stamps, visas, or other permits authorising the bearer to enter, reside, or travel within their territory. Certain jurisdictions permit individuals to clear border controls using identity cards, which typically contain similar personal information.

Different countries impose varying travel document regulations and requirements as part of their border control policies and these may vary based on the traveller's mode of transport. For instance, whilst America does not subject passengers departing by land or most boats to any border control, it does require that passengers departing by air hold a valid passport (or certain specific passport-replacing documents). Consequently, even though travellers departing America by air might not be required to have a passport to enter a certain country, they will be required to have a valid passport booklet to board their flight in order to satisfy American immigration authorities at departure. Similarly, although several countries outside the European Economic Area accept national identity cards issued by its member states for entry, Sweden and Finland do not permit their citizens to depart for countries outside the EEA using solely their identity cards.

Many countries normally allow entry to holders of passports of other countries, sometimes requiring a visa also to be obtained, but this is not an automatic right. Many other additional conditions may apply, such as not being likely to become a public charge for financial or other reasons, and the holder not having been convicted of a crime. Where a country does not recognise another, or is in dispute with it, it may prohibit the use of their passport for travel to that other country, or may prohibit entry to holders of that other country's passports, and sometimes to others who have, for example, visited the other country. Some individuals are subject to sanctions which deny them entry into particular countries.

Travel documents may be requested in other circumstances to confirm identification such as checking into a hotel or when changing money to a local currency. Passports and other travel documents have an expiry date, after which it is no longer recognised, but it is recommended that a passport is valid for at least six months as many airlines deny boarding to passengers whose passport has a shorter expiry date, even if the destination country may not have such a requirement.