Spermicide is a contraceptive substance which immobilizes and kills sperm. It is applied inside the vagina before intercourse to help prevent pregnancy.

Spermicides have been used throughout history from as early as 1850 BC when the Ancient Egyptians used a mix of crocodile dung and fermented dough to prevent pregnancy.

Modern spermicides are clear, unscented, and unflavored substances with lubricating properties. They may take the form of gels, films, creams, suppositories, and foams. Most contain the active ingredient nonoxynol-9.