Indefinite leave to remain (ILR) is an immigration status granted to a person who does not hold the right of abode in the United Kingdom (UK), but who has been admitted to the UK without any time limit on their stay and who is free to take up employment, engage in business, self-employment, or study. When indefinite leave is granted to persons outside the United Kingdom it is known as indefinite leave to enter (ILE).

It approximates to the concept of permanent residency (PR) in other countries, but that term had a different and specific meaning under the EU law on freedom of movement while the UK was in the EU. ILR is granted under UK domestic legislation, PR was (before Brexit) acquired automatically, if certain conditions were met, under EU law.

A person who has indefinite leave to remain, the right of abode or Irish citizenship has settled status if resident in the United Kingdom (all full British citizens have the right of abode). A person with indefinite leave to remain is eligible for access to public funds and welfare in the UK.

Settled status is central to British nationality law, as the most usual route to naturalisation or registration as a British citizen requires that the applicant be settled in the UK. Settled status is also important where a child of non-British citizen parents is born in the UK, as unless at least one parent has settled status the child will not automatically be a British citizen.

A person who is resident in the UK under the Work or Family route will be able to apply for Indefinite Leave to Remain after completing qualifying period of legal stay in the UK.

Indefinite leave can lapse where the holder has stayed outside the United Kingdom for a continuous period of two years and one day or more. It is retained indefinitely if the holder remains resident in the UK with limited absences.