Live oak or evergreen oak is any of a number of oaks in several different sections of the genus Quercus that share the characteristic of evergreen foliage. These oaks are not more closely related to each other than they are to other oaks.

The name live oak comes from the fact that evergreen oaks remain green and "live" throughout winter, when other oaks are dormant and leafless. The name is used mainly in North America, where evergreen oaks are widespread in warmer areas along the Atlantic coast from southeast Virginia to Florida, west along the Gulf Coast to Louisiana and Mexico, and across the southwest to California.

Evergreen oak species are also common in parts of southern Europe and south Asia, and are included in this list for the sake of completeness. These species, although not having "live" in their common names in their countries of origin, are colloquially called live oaks when cultivated in North America.

When the term live oak is used in a specific rather than general sense, it most commonly refers to the group of species under Quercus sect. Virentes, which includes the southern live oak (Quercus virginiana), the first species so named, and an icon of the Old South.

According to the Live Oak Society the oldest southern live oak is believed to be the Seven Sisters Oak located in Mandeville, Louisiana with an estimated age of 500–1,000 years.

The southern live oak is the official state tree of Georgia.

A small grove of live oaks on a prairie is known as a mott.