The (palatine) tonsils are compact ovoid collections of lymphoid tissue located on either side of the throat at the back of the mouth. They are part of the immune system, and are most active in childhood.

Tonsillitis is inflammation of the tonsils, and is caused by viruses or bacteria.

If acute tonsilltis occurs very often, or if chronic tonsillar infection develops, surgical removal of the tonsils (tonsillectomy) may be required to eradicate the infection. Tonsillectomy is one of the most common operations performed for children. Adults may also need their tonsils removed, but this is less frequent.