Sour gum, also known as black gum, is a term that typically refers to two different things:
A type of tree, scientifically known as Nyssa sylvatica, native to eastern North America. It is known for its brilliant red foliage in autumn and its small, blue-black fruits.
A type of chewing gum that is flavored to have a distinctly tart or sour taste. This type of gum often comes in various fruit flavors and is popular among children and teenagers.