Tamu Massif is a seamount in the northwest Pacific Ocean, sitting atop a triple junction of mid-ocean ridges. Tamu Massif is located in the Shatsky Rise about 1,600 km (990 mi) east of Japan. The massif covers an area of about 553,000 square kilometres (214,000 sq mi). Its summit is about 1,980 m (6,500 ft) below the surface of the ocean, and its base extends to about 6.4 km (4.0 mi) deep. It is about 4,460 metres (14,620 ft) tall.

The Shatsky Rise is Earth's third largest oceanic plateau, located in the north-west Pacific Ocean 1,500 km (930 mi) east of Japan. It is one of a series of Pacific Cretaceous large igneous provinces (LIPs) together with Hess Rise, Magellan Rise, and Ontong Java-Manihiki-Hikurangi. It was named for Nikolay Shatsky (1895-1960), a Soviet geologist, expert in tectonics of ancient platforms.