A laissez-passer (from the French let pass) is a travel document issued by a national government or an international treaty organization. When issued by a national government a laissez-passer is often for one-way travel to the issuing country. When issued by an international treaty organization it is often for employee travel on official business.
Some national governments issue laissez-passers to their own nationals as emergency passports. Others issue them to people who are stateless, who are unable to obtain a passport from their own government or whose government is not recognized by the issuing country.
The United Nations and its agencies issue laissez-passer to officials and members of their families for official use. The U.N. laissez-passer is similar to a passport, and is widely recognized worldwide, although some countries will not accept a U.N. laissez-passer as sufficient to gain entry. A U.N. laissez-passer does not generally confer diplomatic immunity, but may confer limited immunities and privileges.
Historically, laissez-passer were commonly issued during wartime and at other periods, literally acting as a pass to allow travel to specific areas, out of war zones or out of the country for various officials, diplomatic agents, or representatives or citizens of third countries. In these contexts, laissez-passer would frequently include quite specific and limited freedom of movement. The form and issuing authority would be more or less standardized depending on the circumstances.