A tampon is a menstrual product designed to absorb blood and vaginal secretions by insertion into the vagina during menstruation. Unlike a pad, it is placed internally, inside of the vaginal canal. Once inserted correctly, a tampon is held in place by the vagina and expands as it soaks up menstrual blood. However, in addition to menstrual blood, the tampon also absorbs the vagina's natural lubrication and bacteria, which can change the normal pH, increasing the risk of infections from the bacterium Staphylococcus aureus, which can lead to toxic shock syndrome (TSS). TSS is a rare but life-threatening infection that requires immediate medical attention.

The majority of tampons sold are made of rayon, or a blend of rayon and cotton, along with synthetic fibers. Some tampons are made out of organic cotton. Tampons are available in several absorbency ratings. Brands include (but are not limited to) Kotex, Playtex, Tampax (Always), O.B., Cora, Lola, Sustain, Honest Company, Seventh Generation, Solimo, and Rael Tampons.

Several countries regulate tampons as medical devices. In the United States, they are considered to be a Class II medical device by the Food and Drug Administration (FDA). They are sometimes used for hemostasis in surgery.