Emergency contraception (EC) is a birth control measure, used after sexual intercourse to prevent pregnancy.

There are different forms of EC. Emergency contraceptive pills (ECPs), sometimes simply referred to as emergency contraceptives (ECs), or the morning-after pill, are medications intended to disrupt or delay ovulation or fertilization, which are necessary for pregnancy.

Intrauterine devices (IUDs) – usually used as a primary contraceptive method – are sometimes used as the most effective form of emergency contraception. However, the use of IUDs for emergency contraception is relatively rare.

Emergency contraception is a birth control measure taken to reduce the risk of pregnancy following unprotected sexual intercourse or when other regular contraceptive measures have not worked properly or have not been used correctly. It is intended to be used occasionally and is not the same as medical abortion. Emergency contraception is offered to women who do not wish to conceive but have had unprotected sex on any day of the menstrual cycle, from day 21 after giving birth, or from day five after abortion or miscarriage. Emergency contraception measures include tablets taken by mouth or the insertion of a copper intrauterine device.

Emergency contraception is not related to medical abortion, which is a drug regimen administered to terminate pregnancies in any trimester.

Emergency contraceptive pills (ECPs) are sometimes referred to as emergency hormonal contraception (EHC). They are taken after unprotected sexual intercourse or the breakage of a condom.

A variety of emergency contraceptive pills are available, including combined estrogen and progestin pills; progestin-only (levonorgestrel, LNG) pills; and antiprogestin (ulipristal acetate or mifepristone) pills. Progestin-only and anti-progestin pills are available as specifically packaged pills for use as emergency contraceptive pills. Emergency contraceptive pills originally contained higher doses of the same hormones (estrogens, progestins, or both) found in regular combined oral contraceptive pills. Combined estrogen and progestin pills are no longer recommended as dedicated emergency contraceptive pills (because this regimen is less effective and caused more nausea), but certain regular combined oral contraceptive pills (taken 2–5 at a time in what was called "the Yuzpe regimen") have also been shown to be effective as emergency contraceptive pills.

Progestin-only emergency contraceptive pills contain levonorgestrel, either as a single tablet (or historically, as a split dose of two tablets taken 12 hours apart), effective up to 72 hours after intercourse. Progestin-only ECPs are sold under many different brand names. Progestin-only ECPs are available over-the-counter (OTC) in many countries (e.g. Australia, Bangladesh, Bulgaria, Canada, Cyprus, Czech Republic, Denmark, Estonia, India, Malta, Netherlands, Norway, Portugal, Romania, Slovakia, South Africa, Sweden, United States), from a pharmacist without a prescription, and available with a prescription in some other countries.