A thin, elastic covering worn on a man's penis during sexual intercourse to catch semen and protect against sexually transmitted diseases (STDs).

When used properly in combination with a vaginal spermicide, a condom is a relatively effective form of contraception. In addition, except for abstinence, condoms are the only effective way to decrease the risk of infection with sexually transmitted diseases (STDs). Many health officials recommend that sexually active adolescents use a condom every time they have sexual intercourse, even when another method of contraception is used. Condoms made of latex are the most effective against STDs.

The combination of a vaginal spermicide and a condom reduce the risk of pregnancy to less that 10%, but a condom alone should not be considered reliable contraction. A condom should always be checked for holes before use, and never used more than once. Before any genital contact, a condom should be unrolled all the way to the base of the penis, allowing a half inch (about 1.25 cm) of empty space at the tip to catch the semen. To create this empty space, the tip of the condom can be pinched as the condom is rolled on. Pinching the tip also prevents air from entering the condom, which can lead to tearing. After intercourse, a man should hold the rim of the condom while withdrawing his penis to prevent semen from spilling.

The only lubricants that can safely be used with a condom are water-based lubricants such as K-Y jelly or contraceptive gels. Oil-base lubricants such as petroleum jelly or baby oil will diminish a condom's effectiveness. A condom in an unopened package will remain effective for several years if not exposed to heat.