Trench mouth is a polymicrobial infection of the gums leading to inflammation, bleeding, deep ulceration and necrotic gum tissue, there may also be fever. It is also known as Vincent's stomatitis or acute necrotizing ulcerative gingivitis (ANUG).

The common name was probably coined during World War I when many soldiers suffered from the condition. There are a number of other theories to the origin of the name.

The condition is caused by an overpopulation of established mouth bacteria due to a number of interacting factors such as poor hygiene, poor diet, other infections and stress. Treatment is by the simple reduction of the bacteria through improved oral cleaning and salt water or hydrogen peroxide-based rinses. Chlorhexidine or Metronidazole can also be used in addition.

Untreated the infection will lead to the loss of teeth from the rotting gums and can spread, as necrotizing stomatitis, into neighbouring tissues in the cheeks, lips or the bones of the jaw. The condition can occur and be especially dangerous in people with weakened immune systems.