Deportation is the removal of a person or group of people by legal decree or force. Most people are deported from countries, but it is also possible to deport people from any area that is controlled by a powerful force with the authority to do so. For instance, exile from a small village could be possible if the village was not ruled by a higher governing group that forbade it. Being deported is often a serious problem for people, particularly if they have nowhere else to go. Most countries now have rules governing who can be deported and why that are made plain and apparent to all citizens, which can be helpful when trying to avoid deportation.

The primary reason people are deported is for punishment. When a person is deemed undesirable in a country due to criminal activity, failure to abide by a visa, or illegal entrance into a country, he or she is vulnerable to being forcible expelled from the country. It is also possible for a person to be deported for philosophical or ethical reasons, such as holding a religious belief or belonging to a social movement, although these are often explained as criminal activity.

Some people accept expulsion from the country as an alternative to other punishment measures. For instance, when the other option is life in prison or death, a person may wish to accept expulsion. When a country deports a person, it does not necessarily imply that the person cannot return as a visitor to the country from which he or she was deported. It simply means that a person is no longer a resident of that country, although other restrictions are often included.

Deportation from areas smaller than countries is somewhat rare. Small areas such as states or provinces often do not have the authority to enforce deportation nor the legal right to do so. Historically, deportation of this kind has occurred and been enforced, but it was often called exile or banishment.

For many people, being deported is a serious emotional and social shock. A person may have no experience with the country to which he or she is deported. This kind of forcible move can split up families, keep a person from his or her assets, and essentially force a person to start over in life. Most people attempt to avoid deportation by obeying local laws.

Many people consider it unfair to deport a person who is born on a country's soil but has parents who are immigrants. Even so, many countries do deport people on the basis of race or parental nationality. What constitutes a fair reason for deportation is entirely cultural. With increased global interaction, subjects of different nations are communicating, traveling, and immigrating at an increased rate. As more populations and groups interact, it becomes more and more important for nations to establish reasonable deportation procedures.