Drug rehabilitation is an umbrella term for a variety of processes by which a person addicted to a drug stops using that drug. These processes can vary from cold turkey to the use of substitute drugs which do not have the same action upon the state of consciousness as the original drug to which the person was addicted.

Many drug rehabilitation programs include attempts to change the patient's behavior. In particular, patients are generally encouraged or required not to associate with friends who still use the addictive substance. Twelve-step programs encourage addicts not only to stop using alcohol or other drugs, but to examine and change habits related to their addictions.

Drug rehabilitation is sometimes part of the criminal justice system. People convicted of minor drug offenses may be sentenced to rehabilitation instead of prison, and those convicted of driving while intoxicated are sometimes required to attend Alcoholics Anonymous meetings.

Substance-abuse rehabilitation is a process of medical and/or psychotherapeutic treatment, for dependency on psychoactive substances.

All of the following are typical objects of dependencies treated:

* alcohol,
* inhaled solvents,
* prescription drugs,
* over-the-counter drugs,
* illegal street drugs
* multiple substances from one or more of those groups

Frequent (but in no case universal) elements of such rehab therapies are:

* twelve-step programs,
* the doctrine that recovery is a permanent process without a culmination, hence the adjective "recovering" before "addict", "alcoholic", etc.
* the doctrine that addicts' attempts at moderation rather than complete abstention inevitably produces relapse (with the slogan "I don't want a drink, I want too many drinks.")

In any case, the intent is to enable the patient to cease their previous level of substance abuse, for the sake of avoiding its legal, social, and physical consequences, especially in extreme abuse; the controversies over seeking moderation or abstinence are almost entirely factual disagreements about whether moderation is achievable by persons with a history of abuse, not about the morality or harm of moderate use by those who practice it with apparent success.