Expulsion from a country of an alien who is living there illegally, or whose presence is considered contrary to the public good.

In the United Kingdom legislation concerning deportation began with the 1905 Aliens Act, giving the government the right to deport an alien convicted of a criminal offence if deportation was recommended by the court. Since the passage of the 1962 Commonwealth Immigration Act the government has been able to deport certain Commonwealth citizens, and subsequent legislation has broadened the grounds for deportation. The 1971 Immigration Act extended the power of the Home Secretary to deport Commonwealth citizens without a court order where deportation was considered to be ‘conducive to the common good’. Since 1973 only UK citizens, and Commonwealth citizens resident in the UK before 1973, have been immune (exempt) from deportation. Grounds for deportation include illegal entry, breach of conditions of admission, and conviction of a criminal offence. A person who has been served a deportation order can appeal to a special tribunal, but the Home Secretary can overrule the advice of the tribunal.