A team of scientists from the University of Houston found that the now-dormant volcano covers an area of about 120,000 square miles and is about 145 million years old.
The massive basalt structure that forms the volcano came from a single point of eruption located at its center, according to lead researcher William Sager.
The volcano’s new name, Tamu Massif, is a combination of the abbreviation for Texas A&M University, where Sager worked for decades, and the French word for "massive."
Tamu Massive’s size eclipses that of Hawaii’s Mauna Loa, which was previously thought to be the world’s largest volcano.
It is thought to have become dormant after a relatively brief period of activity during which it formed in the late Jurassic period.
The volcano's summit lies about 6,500 feet below the surface of the Pacific with much of its base believed to be in waters almost four miles deep.